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According to the most recently available data, approximately 3,400 tonnes of pesticide active ingredients are used in New Zealand agriculture annually.1 While designed to be toxic to pests, they may also affect non-target organisms including humans. Although acute pesticide poisoning has long been a primary health concern, also in New Zealand,2,3 long-term chronic health effects of pesticide exposure have also been demonstrated, including cancer. In the past four decades pesticides have been associated with increased risks of Non-Hodgkin’s lymphoma (NHL), leukaemia, soft tissue sarcoma, cancers of the prostate, pancreas, lung, brain, and ovaries,4 multiple myeloma5,6 and melanoma,7 even at levels that do not induce acute toxicity. The most consistent evidence is for leukaemia and NHL, and also in New Zealand studies of NHL and leukaemia conducted since the 1980s have shown increased risks in farmers, particularly crop farmers and horticultural workers.8–13 Pesticide exposure is the most plausible explanation, although the identification of a causal role for specific pesticides has been difficult. Cancer risks were not limited to one class of pesticides (herbicides, insecticides, fungicides), or to one chemical group (phenoxy herbicides, organochlorine, organophosphate and carbamate pesticides),4–17 with some studies reporting that the risk of NHL increases with the number of different pesticides used, particularly for those pesticides suspected to be carcinogens.14 Recent findings also indicate that in addition to direct genotoxicity, pesticides may cause cancer through other mechanisms, including immunotoxicity, tumor promotion, peroxisome proliferation, hormonal action and metabolic disruption.15

Before specific pesticides are allowed onto the market, regulatory agencies provide a hazard classification of the potential human health effects, including carcinogenicity. Historically, carcinogen hazard classifications have been based mainly on genotoxicity testing and rat or mouse studies. While this has likely restricted the use of many genotoxic chemicals and animal carcinogens, it is now recognised that this is insufficient, and that new data from toxicology and cancer biology need to be used in conjunction with epidemiology to more validly identify human carcinogens.15

With scientific evidence of pesticide carcinogenicity continuously evolving, cancer hazard classifications for specific pesticides also change over time, as do pesticide use profiles as a result of agrichemical developments, legislation and pest resistance. For example, several pesticides currently known or suspected to cause cancer in humans are no longer used in New Zealand since the 1970s and 1980s (Table 1). Pesticide use profiles are also country specific, and estimates of the total use of carcinogenic pesticides can therefore not be projected from one country to another.

The aim of this review is to provide an overview of the number and total quantity (in tonnes of active ingredient) of currently used pesticides in New Zealand that are considered known or suspected human carcinogens by the EPA NZ and other national regulators, and the International Agency for Research on Cancer (IARC). This will aid the discussion about pesticide use and cancer risk in New Zealand and guide efforts to develop effective policies to reduce pesticide exposure and associated cancer risks in agricultural workers and the community.

Table 1: Historic pesticides: pesticides with an IARC evaluation of 2B, 2A or 1, which are no longer used in New Zealand.

1 Never registered in New Zealand.

Methods

Identification of pesticide use in New Zealand

National pesticide use data are not consistently recorded in New Zealand, but periodic ad hoc surveys to quantify its use are available. The most recent assessment of pesticide active ingredients used in New Zealand was published in 2005,1 providing estimates of tonnes of active ingredients used per year in New Zealand agriculture for the 38 most used active ingredients (excluding mineral oil), and also listing minor use active ingredients.1 These estimates were based on data from a survey conducted by The New Zealand Association for Animal Health and Crop Protection (Agcarm), that collected voluntary annual data on sales of pesticides by kilograms of active ingredient (a.i.), supplemented by Statistics New Zealand data collected for New Zealand Customs Service records, on quantities of pesticide product imported.

Carcinogenicity classifications of pesticides

For each of the pesticide active ingredients used in New Zealand, the most recent carcinogenicity classifications of three regulatory agencies were extracted: The New Zealand Environmental Protection Authority [EPA NZ]; the US Environmental Protection Agency [EPA US]; and the European Chemicals Agency [EU]). The classifications of the International Agency for Research on Cancer (IARC) Monograph Programme were also identified. Background information on the classification schemes used by each agency to classify carcinogenicity is summarised below.

New Zealand (EPA NZ)

The New Zealand hazard classifications for pesticides are reported in the Chemical Classification and Information Database (CCID) of the New Zealand Environment Protection Authority (EPA NZ).16 If a substance has any hazardous properties (eg, explosive, flammable, oxidizing, corrosive, toxic or ecotoxic) it is considered a hazardous substance and requires approval under the Hazardous Substances and New Organisms (HSNO) Act 1996.

Figure 1: Hazard classification used for human carcinogenicity in New Zealand.

For each hazardous substance the EPA NZ assigns a hazard classification according to its physical, health and environmental hazards. The cancer classifications used in New Zealand are coded as 6.7A (known or presumed human carcinogen) or 6.7B (suspected human carcinogen) (see Figure 1), a classification framework similar to the Globally Harmonized System of Classification and Labelling of Chemicals.

USA (EPA US)

US carcinogenicity classifications for pesticides are published by the Environmental Protection Agency’s (EPA) Office of Pesticide Programs,17 and classifications are summarised in Chemicals Evaluated for Carcinogenic Potential Annual Cancer Report.18

When assessing possible cancer risk, the EPA considers the carcinogenic potency and the potential for human exposure. The pesticides are evaluated not only to determine if they cause cancer in laboratory animals, but also as to their potential to cause cancer in humans. The factors considered include short-term studies, long-term cancer studies, mutagenicity studies and structure activity concerns. Over time, cancer classification frameworks used by the US EPA have changed as listed in Figure 2, and there is no direct correspondence between the classifications, ie, which classification is used depends on the date of the evaluation.

Figure 2: Cancer classifications used for pesticides in the US.

European Union (EU)

The hazard classifications of pesticides used as plant protection products and evaluated by the European Union are available in the EU Pesticides Database.19 The European Commission evaluates every active substance for safety before it reaches the market. Since 2007, the REACH regulation (Registration, Evaluation, Authorisation and Restriction of Chemicals) regulates the registration, evaluation and authorisation of dangerous substances and the restrictions applicable to them. The European Chemicals Agency (ECHA), established under this regulation is responsible for managing the technical, scientific and administrative aspects of REACH, and for ensuring consistency in its application

The EU uses three codes/categories to classify human carcinogenicity (see Figure 3). The EU Carcinogen 1 classification (A and B combined) is similar to the New Zealand 6.7A classification and the EU Carcinogen 2 classification to the New Zealand 6.7B classification.

Figure 3: Classifications used for human carcinogenicity in the EU.

International Agency for Research on Cancer (IARC)

The International Agency for Research on Cancer (IARC) is the specialised cancer agency of the World Health Organization (WHO). IARC’s Monographs programme on the identification of carcinogenic hazards to humans, critically reviews and evaluates the published scientific evidence on carcinogenic hazards to which humans are exposed, to provide a hazard classification. A list of classifications is available on their website.20 To date, more than 1,000 agents have been reviewed, including several pesticides. Each evaluation is carried out by a working group of independent international experts. The scientific evidence reviewed includes: (1) carcinogenicity in humans (epidemiological studies on cancer in humans exposed to the agent); (2) carcinogenicity in animals (experimental studies on cancer in laboratory animals treated with the agent); and (3) cancer mechanisms (studies of how cancer develops in response to the agent). The scientific evidence is summarised by the working group and the agent classified in one of four categories (see Figure 4).

Figure 4: Hazard classifications used for human carcinogenicity by the IARC Monograph programme.

The classification indicates the weight of the evidence as to whether an agent is capable of causing cancer (technically called “hazard”), and does not measure the likelihood that cancer will occur (technically called “risk”).21

IARC is not a regulator nor does the IARC Monographs programme recommend regulations, legislation or public health interventions, which remain the responsibility of individual governments and other international organisations.

Estimation of use of pesticides classified as suspected human carcinogens

Because the carcinogenicity categories used are somewhat different for each agency, an overarching classification of suspected carcinogenicity to humans was created for the purpose of this review, including: the EPA NZ and EU suspected group; the EPA US probable/likely/possible groups; and the IARC probable/possible groups. The active ingredients classified as suspected human carcinogens by each of the three regulators and IARC were linked to pesticide use data, to estimate the total yearly quantity of suspected carcinogens used in New Zealand agriculture. Minor use active ingredients classified as suspected carcinogens are also listed in this review, but were not included in the estimations, because data on the total weight of active ingredient used per year was not available for these.

Results

In New Zealand, more than 1,000 agrichemical products are currently licensed for use,22 with about 38 active ingredients representing >95% of the total weight of active ingredients applied. The pesticide active ingredients most commonly used in New Zealand agriculture are listed in Table 2, along with the carcinogenicity classifications of three regulatory agencies (EPA NZ, EPA US, EU) and IARC, with shaded cells representing a classification of “suspected human carcinogen” as defined in the methods section. The EPA NZ classifies five, the EU classifies eight, and the EPA US classifies 11 pesticides as suspected human carcinogens. IARC classified four as suspected human carcinogens, but most of the high-use pesticides in New Zealand have not been evaluated by IARC.

Table 2: Active ingredients with current high use in New Zealand1 and human carcinogenicity classifications by the EPA NZ, EPA US, EU and IARC.

1 Approval status: May be used as a component in a product covered by a group standard but it is not approved for use as a chemical in its own right.
2 If the substance is not classified as 6.7A or 6.7B, this is marked as (-).
3 If the substance is not classified as Carc. 1 or 2, this is marked as (-).

Figure 5 provides an overview of the percentage (on a weight basis) of active ingredients used in New Zealand classified as suspected carcinogens, using the agency-specific classifications. Using the EPA NZ classification, 3% of total weight of herbicides, 8% of fungicides and 8% of insecticides are suspected carcinogens, representing 148 tonnes of pesticides (4% of total). Using the EU classification, 10% of total weight of herbicides, 8% of fungicides and 8% of insecticides are suspected carcinogens, representing 288 tonnes of pesticides (8% of total). Using the EPA US classification, 5% of total weight of herbicides, 60% of fungicides, 8% of insecticides and 72% of plant growth regulators are suspected carcinogens, representing 872 tonnes of pesticides (26% of total). The percentage and weight of active ingredients classified as suspected carcinogens by the three regulatory agencies was highest for the fungicides (8–60%; 72–540 tonnes), followed by herbicides (3–10%; 60–200 tonnes), and insecticides (8%, 16 tonnes).

Figure 5: Pie charts of pesticide active ingredients (tonnes/year) used in New Zealand agriculture, with the outer slices representing the percentage classified as suspected carcinogens according to each respective agency’s human carcinogenicity classification.

Weight of pesticide active ingredients used yearly in New Zealand 1:

Percentage of weight of active ingredients that are classified as suspected carcinogens, according to different classifications:

These data indicate that annually New Zealand uses 148–616 tonnes of active pesticide ingredients (4–26% of total) that are classified as suspected human carcinogens, depending on which of the three regulatory agencies the estimate is based. A more sensitive classification is achieved by combining the three regulatory agencies’ classifications and also including the pesticides classified by IARC as possible or probable human carcinogens. This results in a doubling of the upper estimate to 1,730 tonnes, representing 51% of the total weight of pesticide active ingredients used in New Zealand agriculture.

Table 3 lists the active ingredients of minor use pesticides in New Zealand (ie, <1% of total), including only those that at least one of the agencies classified as a suspected human carcinogen. This indicates that an additional 11 herbicides, 15 fungicides and 14 insecticides are listed as a suspected carcinogen by at least one agency.

Table 3: Active ingredients used in New Zealand representing <1% of total active ingredients, that are evaluated as suspected carcinogen by at least one agency.

1 Approval status: May be used as a component in a product covered by a group standard but it is not approved for use as a chemical in its own right.
2 If the substance is not classified as 6.7A or 6.7B, this is marked as (-).
3 If the substance is not classified as Carc. 1 or 2, this is marked as (-).

Discussion

This review of available data on pesticide use in New Zealand and their carcinogenicity classification shows that, although no known human carcinogens are currently used as pesticides in New Zealand, a considerable number of suspected carcinogens are, representing 4–51% of the total weight of pesticide active ingredients applied.

The lowest estimate (4%) is obtained when using the EPA NZ classification, suggesting that New Zealand’s carcinogenicity classifications of pesticides are less stringent compared to other jurisdictions such as the US and the EU. Generally, resources available for chemical re-assessments in small countries such as New Zealand are limited, which may result in out of date classifications that do not incorporate the most recent evidence. Making use of the classifications and evaluations published by the EPA US and the EU, which are more regularly updated, could reduce costs and potentially risk. IARC’s hazard classifications should also be considered, as these are based on the broadest range of peer reviewed scientific data (epidemiology, animal studies and mechanistic data), and as such, more appropriately account for the multiple mechanisms through which pesticides may cause cancer; they also include epidemiological studies, where available, thus representing realistic human exposure situations. However, IARC evaluations are only available for a small number of pesticides and therefore do not provide a complete picture of the carcinogenicity of all registered pesticides, as regulatory agencies aim to do.

Pesticides recently classified by IARC as either 2A or 2B include glyphosate and 2,4-D, both widely used herbicides, and diazinon, an insecticide commonly used on pasture (to combat grass grub and porina), fruit and vegetables. Taking into account the IARC classifications for pesticides therefore greatly impacted on the here presented estimates. While only glyphosate has received considerable media attention,23 it is worth noting that glyphosate is only one in a list of 16 pesticides with high use in New Zealand that have been classified as a suspected carcinogen by at least one of the four here considered agencies.

Many of the pesticides with high use in New Zealand that are classified as suspected carcinogens are no longer approved for use in the EU, including: the herbicides isoproturon, acetochlor, alachlor, trifluralin, linuron; the fungicide tolyfluanid; the insecticides diazinon and carbaryl; and the plant growth regulator hydrogen cyanamide. This may reflect a more precautionary approach of the EU towards pesticides. Pesticide reduction programmes have resulted in substantially reduced overall pesticide use in several European countries, and this also contributes to the reduced use of suspected carcinogens. For example, in Denmark the overall pesticide use has been reported to have reduced from 4,000 to 3,000 tonnes between 1998 and 2000, while suspected carcinogenic pesticide use reduced even more, from approximately 500 tonnes (13% of total) to approximately 30 tonnes (1% of total).24 While Denmark is the only country for which such estimates could be identified from the literature, it does suggest that it is feasible, even within a relatively short time frame, to significantly reduce the use of suspected carcinogens in agriculture.

The percentage as well as weight of active ingredients classified as suspected carcinogens by the three regulatory agencies was highest for fungicides (8–60% of total fungicides weight; 72–540 tonnes), followed by herbicides (3–10%; 60-200 tonnes) and insecticides (8%, 16 tonnes). This suggests that efforts to reduce exposure to suspected carcinogens in New Zealand’s agriculture may need to focus on fungicides. Fungicides are mainly used in the horticultural sectors,1 which incidentally are also the sectors for which elevated NHL and leukemia risks have been reported in New Zealand. Despite many sustainability initiatives, the horticultural sectors continue to be the most intensive users of pesticides on a land area basis (13.2kg a.i./ha), followed by the arable (2.4kg a.i./ha), forestry (0.3kg a.i./ha), and pastoral sectors (0.2kg a.i./ha).1 New Zealand has seen an overall steady increase in pesticide use since the 1960s, with a small decline in the mid and late 1990s, likely resulting from various sustainability initiatives within the fruit sector (eg, KiwiGreen, Integrated Fruit Production).1 This was followed by a 17% increase in tonnes of total pesticide imports over the period 1999–2003,1 with herbicides increasing by 42%, fungicides by 10%, while insecticides decreased by 41%.1

A limitation of the here presented estimates is that they were based on pesticide use data published in 2005: the last date for which comprehensive data were available. Pesticide use profiles have likely changed since then, although New Zealand legislative changes for the here listed pesticides have been minor: only the fungicide benomyl, which had relatively low use in 2005, has been revoked since then, and all 16 high-use pesticides suspected to be human carcinogens have continued to be commonly used in New Zealand. The here presented estimates are therefore likely to sufficiently reflect the current use of pesticides in New Zealand. To enable assessing time-trends in the use of pesticides in New Zealand’s agriculture, including the use of suspected carcinogens, an investment will have to be made in regularly updating detailed data on pesticide use. When assessing time trends using tonnage it should be noted that newer pesticides may be active at lower doses (g per ha, rather than kg per ha for many of the older pesticides), so that a reduction in gross weight may not necessarily equate to reductions in risks to health.

In summary, this review indicates that a large volume of pesticides used in New Zealand are suspected carcinogens. As a result, we will likely continue to see an increased risk of cancer, in particular leukaemias and lymphomas, for people who frequently use pesticides as part of their work. A pesticide risk reduction programme, as has successfully been implemented in several other countries (eg, Denmark), will likely reduce this risk, while also reducing the risk of several other health effects associated with pesticides (eg, impaired neurobehavioral function, neurodegenerative diseases, impaired fertility). In the absence of this, pesticide risk reduction will continue to depend largely on voluntary action by its users, which is unlikely to be sufficiently effective. Efforts to reduce the health risks of pesticides require government leadership, through for example the Ministry of Health’s National Cancer Action Plan, WorkSafe’s Strategic Plan for Work-Related Health, and NZ EPA’s regulation of pesticides. Medical professionals may also play a role by: (1) considering patients’ occupations and associated hazardous exposures; (2) communicating potential risks associated with pesticides to patients and the general public; and (3) promoting and supporting patients’ efforts to reduce pesticide exposure to themselves and their families.

Summary

Abstract

Aim

To estimate the number and weight of pesticides used in New Zealand agriculture that are classified as known or suspected human carcinogens.

Method

The yearly usage of active ingredients was extracted from the most recent (2005) report on pesticide use. For each active ingredient, the carcinogenicity classification of three regulatory agencies (New Zealand Environmental Protection Authority [EPA NZ], US Environmental Protection Agency, European Chemicals Agency) was extracted. The International Agency for Research on Cancer (IARC) Monograph Programme’s classifications were also considered. Total tonnes of active ingredients were calculated according to each classification.

Results

None of the pesticides are classified as known human carcinogens. In total, 56 active ingredients are listed as suspected carcinogens by at least one of the four agencies, including 16 high-use ingredients, representing up to 51% of the total yearly quantity. Agency-specific estimates ranged between 4–26% (148–872 tonnes) with the EPA NZ classification yielding the lowest estimate. The suspected carcinogen weight was highest for fungicides (estimates based on the three regulatory agencies ranged between 72–540 tonnes), followed by herbicides (60–200 tonnes) and insecticides (16 tonnes).

Conclusion

New Zealand’s use of pesticides that are suspected carcinogens is high. Efforts to increase awareness and reduce exposure need to be considered.

Author Information

Andrea Martine 't Mannetje, Centre for Public Health Research, Massey University, Wellington.

Acknowledgements

Correspondence

Dr Andrea Martine 't Mannetje, Centre for Public Health Research, Massey University, Wellington 6140.

Correspondence Email

a.mannetje@massey.ac.nz

Competing Interests

Nil.

1. Manktelow D, Stevens P, Walker J, et al. Trends in Pesticide Use in New Zealand : 2004. 2005.

2. Firth H, Beasley M, Ashton J. Occupational calls to the New Zealand National Poisons Centre for the years 1990 to 1998. Journal of Occupational Health and Safety - Australia and New Zealand. 2000; 16:131–136.

3. Firth H, Herbison P, McBride D, Feyer AM. Health of farmers in southland: an overview. N Z Med J. Sep 28 2001; 114(1140):426–428.

4. Alavanja MC, Hoppin JA, Kamel F. Health effects of chronic pesticide exposure: cancer and neurotoxicity. Annu Rev Public Health. 2004; 25:155–197.

5. Frost G, Brown T, Harding AH. Mortality and cancer incidence among British agricultural pesticide users. Occup Med (Lond). Aug 2011; 61(5):303–310.

6. Kachuri L, Demers PA, Blair A, et al. Multiple pesticide exposures and the risk of multiple myeloma in Canadian men. Int J Cancer. Oct 15 2013; 133(8):1846–1858.

7. Dennis LK, Lynch CF, Sandler DP, Alavanja MC. Pesticide use and cutaneous melanoma in pesticide applicators in the agricultural heath study. Environ Health Perspect. Jun 2010; 118(6):812–817.

8. Pearce NE, Sheppard RA, Howard JK, Fraser J, Lilley BM. Leukemia among New Zealand agricultural workers. A cancer registry-based study. Am J Epidemiol. Sep 1986; 124(3):402–409.

9. Pearce NE, Sheppard RA, Smith AH, Teague CA. Non-Hodgkin's lymphoma and farming: an expanded case-control study. Int J Cancer. Feb 15 1987; 39(2):155–161.

10. Pearce NE, Smith AH, Fisher DO. Malignant lymphoma and multiple myeloma linked with agricultural occupations in a New Zealand Cancer Registry-based study. Am J Epidemiol. Feb 1985; 121(2):225–237.

11. t Mannetje A, Dryson E, Walls C, et al. High risk occupations for non-Hodgkin's lymphoma in New Zealand: case-control study. Occup Environ Med. May 2008; 65(5):354–363.

12. t Mannetje A, Eng A, Pearce N. Farming, growing up on a farm, and haematological cancer mortality. Occup Environ Med. Feb 2012; 69(2):126–132.

13. McLean D, Mannetje A, Dryson E, et al. Leukaemia and occupation: a New Zealand Cancer Registry-based case-control Study. Int J Epidemiol. Apr 2009; 38(2):594–606.

14. Hohenadel K, Harris SA, McLaughlin JR, et al. Exposure to multiple pesticides and risk of non-Hodgkin lymphoma in men from six Canadian provinces. Int J Environ Res Public Health. Jun 2011; 8(6):2320–2330.

15. Alavanja MC, Ross MK, Bonner MR. Increased cancer burden among pesticide applicators and others due to pesticide exposure. CA Cancer J Clin. Mar-Apr 2013; 63(2):120–142.

16. Chemical Classification and Information Database (CCID). www.epa.govt.nz/database-search/chemical-classification-and-information-database-ccid/ 2018.

17. Evaluating Pesticides for Carcinogenic Potential http://www.epa.gov/pesticide-science-and-assessing-pesticide-risks/evaluating-pesticides-carcinogenic-potential 2018.

18. Chemicals Evaluated for Carcinogenic Potential Annual Cancer Report 2018: US Environmental Protection Agency Office of Pesticide Programs 2018.

19. EU Pesticides database. Search active substances. http://ec.europa.eu/food/plant/pesticides/eu-pesticides-database/public/?event=activesubstance.selection&language=EN

20. International Agency for Research on Cancer. IARC Monographs on the Evaluation of Carcinogenic Risks to Humans. List of classifications, volumes 1-123. https://monographs.iarc.fr/list-of-classifications-volumes/ 2018.

21. International Agency for Research on Cancer. IARC Monographs Questions and Answers. www.iarc.fr/en/media-centre/iarcnews/pdf/Monographs-Q&A.pdf 2018.

22. Young S. New Zealand Novachem Agricultural Manual. Agrimedia, Christchurch, New Zealand 2013.

23. Douwes J, t Mannetje A, McLean D, Pearce N, Woodward A, Potter JD. Carcinogenicity of glyphosate: why is New Zealand's EPA lost in the weeds? N Z Med J. Mar 23 2018; 131(1472):82–89.

24. PAN Germany and PAN UK, in cooperation with PAN Europe. Pesticide Reduction Programmes in Germany and the UK Experiences and Contributions within a Europe wide Approach. Workshop report. http://www.pan-germany.org/download/pure_conf_0507.pdf 2005.

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According to the most recently available data, approximately 3,400 tonnes of pesticide active ingredients are used in New Zealand agriculture annually.1 While designed to be toxic to pests, they may also affect non-target organisms including humans. Although acute pesticide poisoning has long been a primary health concern, also in New Zealand,2,3 long-term chronic health effects of pesticide exposure have also been demonstrated, including cancer. In the past four decades pesticides have been associated with increased risks of Non-Hodgkin’s lymphoma (NHL), leukaemia, soft tissue sarcoma, cancers of the prostate, pancreas, lung, brain, and ovaries,4 multiple myeloma5,6 and melanoma,7 even at levels that do not induce acute toxicity. The most consistent evidence is for leukaemia and NHL, and also in New Zealand studies of NHL and leukaemia conducted since the 1980s have shown increased risks in farmers, particularly crop farmers and horticultural workers.8–13 Pesticide exposure is the most plausible explanation, although the identification of a causal role for specific pesticides has been difficult. Cancer risks were not limited to one class of pesticides (herbicides, insecticides, fungicides), or to one chemical group (phenoxy herbicides, organochlorine, organophosphate and carbamate pesticides),4–17 with some studies reporting that the risk of NHL increases with the number of different pesticides used, particularly for those pesticides suspected to be carcinogens.14 Recent findings also indicate that in addition to direct genotoxicity, pesticides may cause cancer through other mechanisms, including immunotoxicity, tumor promotion, peroxisome proliferation, hormonal action and metabolic disruption.15

Before specific pesticides are allowed onto the market, regulatory agencies provide a hazard classification of the potential human health effects, including carcinogenicity. Historically, carcinogen hazard classifications have been based mainly on genotoxicity testing and rat or mouse studies. While this has likely restricted the use of many genotoxic chemicals and animal carcinogens, it is now recognised that this is insufficient, and that new data from toxicology and cancer biology need to be used in conjunction with epidemiology to more validly identify human carcinogens.15

With scientific evidence of pesticide carcinogenicity continuously evolving, cancer hazard classifications for specific pesticides also change over time, as do pesticide use profiles as a result of agrichemical developments, legislation and pest resistance. For example, several pesticides currently known or suspected to cause cancer in humans are no longer used in New Zealand since the 1970s and 1980s (Table 1). Pesticide use profiles are also country specific, and estimates of the total use of carcinogenic pesticides can therefore not be projected from one country to another.

The aim of this review is to provide an overview of the number and total quantity (in tonnes of active ingredient) of currently used pesticides in New Zealand that are considered known or suspected human carcinogens by the EPA NZ and other national regulators, and the International Agency for Research on Cancer (IARC). This will aid the discussion about pesticide use and cancer risk in New Zealand and guide efforts to develop effective policies to reduce pesticide exposure and associated cancer risks in agricultural workers and the community.

Table 1: Historic pesticides: pesticides with an IARC evaluation of 2B, 2A or 1, which are no longer used in New Zealand.

1 Never registered in New Zealand.

Methods

Identification of pesticide use in New Zealand

National pesticide use data are not consistently recorded in New Zealand, but periodic ad hoc surveys to quantify its use are available. The most recent assessment of pesticide active ingredients used in New Zealand was published in 2005,1 providing estimates of tonnes of active ingredients used per year in New Zealand agriculture for the 38 most used active ingredients (excluding mineral oil), and also listing minor use active ingredients.1 These estimates were based on data from a survey conducted by The New Zealand Association for Animal Health and Crop Protection (Agcarm), that collected voluntary annual data on sales of pesticides by kilograms of active ingredient (a.i.), supplemented by Statistics New Zealand data collected for New Zealand Customs Service records, on quantities of pesticide product imported.

Carcinogenicity classifications of pesticides

For each of the pesticide active ingredients used in New Zealand, the most recent carcinogenicity classifications of three regulatory agencies were extracted: The New Zealand Environmental Protection Authority [EPA NZ]; the US Environmental Protection Agency [EPA US]; and the European Chemicals Agency [EU]). The classifications of the International Agency for Research on Cancer (IARC) Monograph Programme were also identified. Background information on the classification schemes used by each agency to classify carcinogenicity is summarised below.

New Zealand (EPA NZ)

The New Zealand hazard classifications for pesticides are reported in the Chemical Classification and Information Database (CCID) of the New Zealand Environment Protection Authority (EPA NZ).16 If a substance has any hazardous properties (eg, explosive, flammable, oxidizing, corrosive, toxic or ecotoxic) it is considered a hazardous substance and requires approval under the Hazardous Substances and New Organisms (HSNO) Act 1996.

Figure 1: Hazard classification used for human carcinogenicity in New Zealand.

For each hazardous substance the EPA NZ assigns a hazard classification according to its physical, health and environmental hazards. The cancer classifications used in New Zealand are coded as 6.7A (known or presumed human carcinogen) or 6.7B (suspected human carcinogen) (see Figure 1), a classification framework similar to the Globally Harmonized System of Classification and Labelling of Chemicals.

USA (EPA US)

US carcinogenicity classifications for pesticides are published by the Environmental Protection Agency’s (EPA) Office of Pesticide Programs,17 and classifications are summarised in Chemicals Evaluated for Carcinogenic Potential Annual Cancer Report.18

When assessing possible cancer risk, the EPA considers the carcinogenic potency and the potential for human exposure. The pesticides are evaluated not only to determine if they cause cancer in laboratory animals, but also as to their potential to cause cancer in humans. The factors considered include short-term studies, long-term cancer studies, mutagenicity studies and structure activity concerns. Over time, cancer classification frameworks used by the US EPA have changed as listed in Figure 2, and there is no direct correspondence between the classifications, ie, which classification is used depends on the date of the evaluation.

Figure 2: Cancer classifications used for pesticides in the US.

European Union (EU)

The hazard classifications of pesticides used as plant protection products and evaluated by the European Union are available in the EU Pesticides Database.19 The European Commission evaluates every active substance for safety before it reaches the market. Since 2007, the REACH regulation (Registration, Evaluation, Authorisation and Restriction of Chemicals) regulates the registration, evaluation and authorisation of dangerous substances and the restrictions applicable to them. The European Chemicals Agency (ECHA), established under this regulation is responsible for managing the technical, scientific and administrative aspects of REACH, and for ensuring consistency in its application

The EU uses three codes/categories to classify human carcinogenicity (see Figure 3). The EU Carcinogen 1 classification (A and B combined) is similar to the New Zealand 6.7A classification and the EU Carcinogen 2 classification to the New Zealand 6.7B classification.

Figure 3: Classifications used for human carcinogenicity in the EU.

International Agency for Research on Cancer (IARC)

The International Agency for Research on Cancer (IARC) is the specialised cancer agency of the World Health Organization (WHO). IARC’s Monographs programme on the identification of carcinogenic hazards to humans, critically reviews and evaluates the published scientific evidence on carcinogenic hazards to which humans are exposed, to provide a hazard classification. A list of classifications is available on their website.20 To date, more than 1,000 agents have been reviewed, including several pesticides. Each evaluation is carried out by a working group of independent international experts. The scientific evidence reviewed includes: (1) carcinogenicity in humans (epidemiological studies on cancer in humans exposed to the agent); (2) carcinogenicity in animals (experimental studies on cancer in laboratory animals treated with the agent); and (3) cancer mechanisms (studies of how cancer develops in response to the agent). The scientific evidence is summarised by the working group and the agent classified in one of four categories (see Figure 4).

Figure 4: Hazard classifications used for human carcinogenicity by the IARC Monograph programme.

The classification indicates the weight of the evidence as to whether an agent is capable of causing cancer (technically called “hazard”), and does not measure the likelihood that cancer will occur (technically called “risk”).21

IARC is not a regulator nor does the IARC Monographs programme recommend regulations, legislation or public health interventions, which remain the responsibility of individual governments and other international organisations.

Estimation of use of pesticides classified as suspected human carcinogens

Because the carcinogenicity categories used are somewhat different for each agency, an overarching classification of suspected carcinogenicity to humans was created for the purpose of this review, including: the EPA NZ and EU suspected group; the EPA US probable/likely/possible groups; and the IARC probable/possible groups. The active ingredients classified as suspected human carcinogens by each of the three regulators and IARC were linked to pesticide use data, to estimate the total yearly quantity of suspected carcinogens used in New Zealand agriculture. Minor use active ingredients classified as suspected carcinogens are also listed in this review, but were not included in the estimations, because data on the total weight of active ingredient used per year was not available for these.

Results

In New Zealand, more than 1,000 agrichemical products are currently licensed for use,22 with about 38 active ingredients representing >95% of the total weight of active ingredients applied. The pesticide active ingredients most commonly used in New Zealand agriculture are listed in Table 2, along with the carcinogenicity classifications of three regulatory agencies (EPA NZ, EPA US, EU) and IARC, with shaded cells representing a classification of “suspected human carcinogen” as defined in the methods section. The EPA NZ classifies five, the EU classifies eight, and the EPA US classifies 11 pesticides as suspected human carcinogens. IARC classified four as suspected human carcinogens, but most of the high-use pesticides in New Zealand have not been evaluated by IARC.

Table 2: Active ingredients with current high use in New Zealand1 and human carcinogenicity classifications by the EPA NZ, EPA US, EU and IARC.

1 Approval status: May be used as a component in a product covered by a group standard but it is not approved for use as a chemical in its own right.
2 If the substance is not classified as 6.7A or 6.7B, this is marked as (-).
3 If the substance is not classified as Carc. 1 or 2, this is marked as (-).

Figure 5 provides an overview of the percentage (on a weight basis) of active ingredients used in New Zealand classified as suspected carcinogens, using the agency-specific classifications. Using the EPA NZ classification, 3% of total weight of herbicides, 8% of fungicides and 8% of insecticides are suspected carcinogens, representing 148 tonnes of pesticides (4% of total). Using the EU classification, 10% of total weight of herbicides, 8% of fungicides and 8% of insecticides are suspected carcinogens, representing 288 tonnes of pesticides (8% of total). Using the EPA US classification, 5% of total weight of herbicides, 60% of fungicides, 8% of insecticides and 72% of plant growth regulators are suspected carcinogens, representing 872 tonnes of pesticides (26% of total). The percentage and weight of active ingredients classified as suspected carcinogens by the three regulatory agencies was highest for the fungicides (8–60%; 72–540 tonnes), followed by herbicides (3–10%; 60–200 tonnes), and insecticides (8%, 16 tonnes).

Figure 5: Pie charts of pesticide active ingredients (tonnes/year) used in New Zealand agriculture, with the outer slices representing the percentage classified as suspected carcinogens according to each respective agency’s human carcinogenicity classification.

Weight of pesticide active ingredients used yearly in New Zealand 1:

Percentage of weight of active ingredients that are classified as suspected carcinogens, according to different classifications:

These data indicate that annually New Zealand uses 148–616 tonnes of active pesticide ingredients (4–26% of total) that are classified as suspected human carcinogens, depending on which of the three regulatory agencies the estimate is based. A more sensitive classification is achieved by combining the three regulatory agencies’ classifications and also including the pesticides classified by IARC as possible or probable human carcinogens. This results in a doubling of the upper estimate to 1,730 tonnes, representing 51% of the total weight of pesticide active ingredients used in New Zealand agriculture.

Table 3 lists the active ingredients of minor use pesticides in New Zealand (ie, <1% of total), including only those that at least one of the agencies classified as a suspected human carcinogen. This indicates that an additional 11 herbicides, 15 fungicides and 14 insecticides are listed as a suspected carcinogen by at least one agency.

Table 3: Active ingredients used in New Zealand representing <1% of total active ingredients, that are evaluated as suspected carcinogen by at least one agency.

1 Approval status: May be used as a component in a product covered by a group standard but it is not approved for use as a chemical in its own right.
2 If the substance is not classified as 6.7A or 6.7B, this is marked as (-).
3 If the substance is not classified as Carc. 1 or 2, this is marked as (-).

Discussion

This review of available data on pesticide use in New Zealand and their carcinogenicity classification shows that, although no known human carcinogens are currently used as pesticides in New Zealand, a considerable number of suspected carcinogens are, representing 4–51% of the total weight of pesticide active ingredients applied.

The lowest estimate (4%) is obtained when using the EPA NZ classification, suggesting that New Zealand’s carcinogenicity classifications of pesticides are less stringent compared to other jurisdictions such as the US and the EU. Generally, resources available for chemical re-assessments in small countries such as New Zealand are limited, which may result in out of date classifications that do not incorporate the most recent evidence. Making use of the classifications and evaluations published by the EPA US and the EU, which are more regularly updated, could reduce costs and potentially risk. IARC’s hazard classifications should also be considered, as these are based on the broadest range of peer reviewed scientific data (epidemiology, animal studies and mechanistic data), and as such, more appropriately account for the multiple mechanisms through which pesticides may cause cancer; they also include epidemiological studies, where available, thus representing realistic human exposure situations. However, IARC evaluations are only available for a small number of pesticides and therefore do not provide a complete picture of the carcinogenicity of all registered pesticides, as regulatory agencies aim to do.

Pesticides recently classified by IARC as either 2A or 2B include glyphosate and 2,4-D, both widely used herbicides, and diazinon, an insecticide commonly used on pasture (to combat grass grub and porina), fruit and vegetables. Taking into account the IARC classifications for pesticides therefore greatly impacted on the here presented estimates. While only glyphosate has received considerable media attention,23 it is worth noting that glyphosate is only one in a list of 16 pesticides with high use in New Zealand that have been classified as a suspected carcinogen by at least one of the four here considered agencies.

Many of the pesticides with high use in New Zealand that are classified as suspected carcinogens are no longer approved for use in the EU, including: the herbicides isoproturon, acetochlor, alachlor, trifluralin, linuron; the fungicide tolyfluanid; the insecticides diazinon and carbaryl; and the plant growth regulator hydrogen cyanamide. This may reflect a more precautionary approach of the EU towards pesticides. Pesticide reduction programmes have resulted in substantially reduced overall pesticide use in several European countries, and this also contributes to the reduced use of suspected carcinogens. For example, in Denmark the overall pesticide use has been reported to have reduced from 4,000 to 3,000 tonnes between 1998 and 2000, while suspected carcinogenic pesticide use reduced even more, from approximately 500 tonnes (13% of total) to approximately 30 tonnes (1% of total).24 While Denmark is the only country for which such estimates could be identified from the literature, it does suggest that it is feasible, even within a relatively short time frame, to significantly reduce the use of suspected carcinogens in agriculture.

The percentage as well as weight of active ingredients classified as suspected carcinogens by the three regulatory agencies was highest for fungicides (8–60% of total fungicides weight; 72–540 tonnes), followed by herbicides (3–10%; 60-200 tonnes) and insecticides (8%, 16 tonnes). This suggests that efforts to reduce exposure to suspected carcinogens in New Zealand’s agriculture may need to focus on fungicides. Fungicides are mainly used in the horticultural sectors,1 which incidentally are also the sectors for which elevated NHL and leukemia risks have been reported in New Zealand. Despite many sustainability initiatives, the horticultural sectors continue to be the most intensive users of pesticides on a land area basis (13.2kg a.i./ha), followed by the arable (2.4kg a.i./ha), forestry (0.3kg a.i./ha), and pastoral sectors (0.2kg a.i./ha).1 New Zealand has seen an overall steady increase in pesticide use since the 1960s, with a small decline in the mid and late 1990s, likely resulting from various sustainability initiatives within the fruit sector (eg, KiwiGreen, Integrated Fruit Production).1 This was followed by a 17% increase in tonnes of total pesticide imports over the period 1999–2003,1 with herbicides increasing by 42%, fungicides by 10%, while insecticides decreased by 41%.1

A limitation of the here presented estimates is that they were based on pesticide use data published in 2005: the last date for which comprehensive data were available. Pesticide use profiles have likely changed since then, although New Zealand legislative changes for the here listed pesticides have been minor: only the fungicide benomyl, which had relatively low use in 2005, has been revoked since then, and all 16 high-use pesticides suspected to be human carcinogens have continued to be commonly used in New Zealand. The here presented estimates are therefore likely to sufficiently reflect the current use of pesticides in New Zealand. To enable assessing time-trends in the use of pesticides in New Zealand’s agriculture, including the use of suspected carcinogens, an investment will have to be made in regularly updating detailed data on pesticide use. When assessing time trends using tonnage it should be noted that newer pesticides may be active at lower doses (g per ha, rather than kg per ha for many of the older pesticides), so that a reduction in gross weight may not necessarily equate to reductions in risks to health.

In summary, this review indicates that a large volume of pesticides used in New Zealand are suspected carcinogens. As a result, we will likely continue to see an increased risk of cancer, in particular leukaemias and lymphomas, for people who frequently use pesticides as part of their work. A pesticide risk reduction programme, as has successfully been implemented in several other countries (eg, Denmark), will likely reduce this risk, while also reducing the risk of several other health effects associated with pesticides (eg, impaired neurobehavioral function, neurodegenerative diseases, impaired fertility). In the absence of this, pesticide risk reduction will continue to depend largely on voluntary action by its users, which is unlikely to be sufficiently effective. Efforts to reduce the health risks of pesticides require government leadership, through for example the Ministry of Health’s National Cancer Action Plan, WorkSafe’s Strategic Plan for Work-Related Health, and NZ EPA’s regulation of pesticides. Medical professionals may also play a role by: (1) considering patients’ occupations and associated hazardous exposures; (2) communicating potential risks associated with pesticides to patients and the general public; and (3) promoting and supporting patients’ efforts to reduce pesticide exposure to themselves and their families.

Summary

Abstract

Aim

To estimate the number and weight of pesticides used in New Zealand agriculture that are classified as known or suspected human carcinogens.

Method

The yearly usage of active ingredients was extracted from the most recent (2005) report on pesticide use. For each active ingredient, the carcinogenicity classification of three regulatory agencies (New Zealand Environmental Protection Authority [EPA NZ], US Environmental Protection Agency, European Chemicals Agency) was extracted. The International Agency for Research on Cancer (IARC) Monograph Programme’s classifications were also considered. Total tonnes of active ingredients were calculated according to each classification.

Results

None of the pesticides are classified as known human carcinogens. In total, 56 active ingredients are listed as suspected carcinogens by at least one of the four agencies, including 16 high-use ingredients, representing up to 51% of the total yearly quantity. Agency-specific estimates ranged between 4–26% (148–872 tonnes) with the EPA NZ classification yielding the lowest estimate. The suspected carcinogen weight was highest for fungicides (estimates based on the three regulatory agencies ranged between 72–540 tonnes), followed by herbicides (60–200 tonnes) and insecticides (16 tonnes).

Conclusion

New Zealand’s use of pesticides that are suspected carcinogens is high. Efforts to increase awareness and reduce exposure need to be considered.

Author Information

Andrea Martine 't Mannetje, Centre for Public Health Research, Massey University, Wellington.

Acknowledgements

Correspondence

Dr Andrea Martine 't Mannetje, Centre for Public Health Research, Massey University, Wellington 6140.

Correspondence Email

a.mannetje@massey.ac.nz

Competing Interests

Nil.

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5. Frost G, Brown T, Harding AH. Mortality and cancer incidence among British agricultural pesticide users. Occup Med (Lond). Aug 2011; 61(5):303–310.

6. Kachuri L, Demers PA, Blair A, et al. Multiple pesticide exposures and the risk of multiple myeloma in Canadian men. Int J Cancer. Oct 15 2013; 133(8):1846–1858.

7. Dennis LK, Lynch CF, Sandler DP, Alavanja MC. Pesticide use and cutaneous melanoma in pesticide applicators in the agricultural heath study. Environ Health Perspect. Jun 2010; 118(6):812–817.

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11. t Mannetje A, Dryson E, Walls C, et al. High risk occupations for non-Hodgkin's lymphoma in New Zealand: case-control study. Occup Environ Med. May 2008; 65(5):354–363.

12. t Mannetje A, Eng A, Pearce N. Farming, growing up on a farm, and haematological cancer mortality. Occup Environ Med. Feb 2012; 69(2):126–132.

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14. Hohenadel K, Harris SA, McLaughlin JR, et al. Exposure to multiple pesticides and risk of non-Hodgkin lymphoma in men from six Canadian provinces. Int J Environ Res Public Health. Jun 2011; 8(6):2320–2330.

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16. Chemical Classification and Information Database (CCID). www.epa.govt.nz/database-search/chemical-classification-and-information-database-ccid/ 2018.

17. Evaluating Pesticides for Carcinogenic Potential http://www.epa.gov/pesticide-science-and-assessing-pesticide-risks/evaluating-pesticides-carcinogenic-potential 2018.

18. Chemicals Evaluated for Carcinogenic Potential Annual Cancer Report 2018: US Environmental Protection Agency Office of Pesticide Programs 2018.

19. EU Pesticides database. Search active substances. http://ec.europa.eu/food/plant/pesticides/eu-pesticides-database/public/?event=activesubstance.selection&language=EN

20. International Agency for Research on Cancer. IARC Monographs on the Evaluation of Carcinogenic Risks to Humans. List of classifications, volumes 1-123. https://monographs.iarc.fr/list-of-classifications-volumes/ 2018.

21. International Agency for Research on Cancer. IARC Monographs Questions and Answers. www.iarc.fr/en/media-centre/iarcnews/pdf/Monographs-Q&A.pdf 2018.

22. Young S. New Zealand Novachem Agricultural Manual. Agrimedia, Christchurch, New Zealand 2013.

23. Douwes J, t Mannetje A, McLean D, Pearce N, Woodward A, Potter JD. Carcinogenicity of glyphosate: why is New Zealand's EPA lost in the weeds? N Z Med J. Mar 23 2018; 131(1472):82–89.

24. PAN Germany and PAN UK, in cooperation with PAN Europe. Pesticide Reduction Programmes in Germany and the UK Experiences and Contributions within a Europe wide Approach. Workshop report. http://www.pan-germany.org/download/pure_conf_0507.pdf 2005.

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According to the most recently available data, approximately 3,400 tonnes of pesticide active ingredients are used in New Zealand agriculture annually.1 While designed to be toxic to pests, they may also affect non-target organisms including humans. Although acute pesticide poisoning has long been a primary health concern, also in New Zealand,2,3 long-term chronic health effects of pesticide exposure have also been demonstrated, including cancer. In the past four decades pesticides have been associated with increased risks of Non-Hodgkin’s lymphoma (NHL), leukaemia, soft tissue sarcoma, cancers of the prostate, pancreas, lung, brain, and ovaries,4 multiple myeloma5,6 and melanoma,7 even at levels that do not induce acute toxicity. The most consistent evidence is for leukaemia and NHL, and also in New Zealand studies of NHL and leukaemia conducted since the 1980s have shown increased risks in farmers, particularly crop farmers and horticultural workers.8–13 Pesticide exposure is the most plausible explanation, although the identification of a causal role for specific pesticides has been difficult. Cancer risks were not limited to one class of pesticides (herbicides, insecticides, fungicides), or to one chemical group (phenoxy herbicides, organochlorine, organophosphate and carbamate pesticides),4–17 with some studies reporting that the risk of NHL increases with the number of different pesticides used, particularly for those pesticides suspected to be carcinogens.14 Recent findings also indicate that in addition to direct genotoxicity, pesticides may cause cancer through other mechanisms, including immunotoxicity, tumor promotion, peroxisome proliferation, hormonal action and metabolic disruption.15

Before specific pesticides are allowed onto the market, regulatory agencies provide a hazard classification of the potential human health effects, including carcinogenicity. Historically, carcinogen hazard classifications have been based mainly on genotoxicity testing and rat or mouse studies. While this has likely restricted the use of many genotoxic chemicals and animal carcinogens, it is now recognised that this is insufficient, and that new data from toxicology and cancer biology need to be used in conjunction with epidemiology to more validly identify human carcinogens.15

With scientific evidence of pesticide carcinogenicity continuously evolving, cancer hazard classifications for specific pesticides also change over time, as do pesticide use profiles as a result of agrichemical developments, legislation and pest resistance. For example, several pesticides currently known or suspected to cause cancer in humans are no longer used in New Zealand since the 1970s and 1980s (Table 1). Pesticide use profiles are also country specific, and estimates of the total use of carcinogenic pesticides can therefore not be projected from one country to another.

The aim of this review is to provide an overview of the number and total quantity (in tonnes of active ingredient) of currently used pesticides in New Zealand that are considered known or suspected human carcinogens by the EPA NZ and other national regulators, and the International Agency for Research on Cancer (IARC). This will aid the discussion about pesticide use and cancer risk in New Zealand and guide efforts to develop effective policies to reduce pesticide exposure and associated cancer risks in agricultural workers and the community.

Table 1: Historic pesticides: pesticides with an IARC evaluation of 2B, 2A or 1, which are no longer used in New Zealand.

1 Never registered in New Zealand.

Methods

Identification of pesticide use in New Zealand

National pesticide use data are not consistently recorded in New Zealand, but periodic ad hoc surveys to quantify its use are available. The most recent assessment of pesticide active ingredients used in New Zealand was published in 2005,1 providing estimates of tonnes of active ingredients used per year in New Zealand agriculture for the 38 most used active ingredients (excluding mineral oil), and also listing minor use active ingredients.1 These estimates were based on data from a survey conducted by The New Zealand Association for Animal Health and Crop Protection (Agcarm), that collected voluntary annual data on sales of pesticides by kilograms of active ingredient (a.i.), supplemented by Statistics New Zealand data collected for New Zealand Customs Service records, on quantities of pesticide product imported.

Carcinogenicity classifications of pesticides

For each of the pesticide active ingredients used in New Zealand, the most recent carcinogenicity classifications of three regulatory agencies were extracted: The New Zealand Environmental Protection Authority [EPA NZ]; the US Environmental Protection Agency [EPA US]; and the European Chemicals Agency [EU]). The classifications of the International Agency for Research on Cancer (IARC) Monograph Programme were also identified. Background information on the classification schemes used by each agency to classify carcinogenicity is summarised below.

New Zealand (EPA NZ)

The New Zealand hazard classifications for pesticides are reported in the Chemical Classification and Information Database (CCID) of the New Zealand Environment Protection Authority (EPA NZ).16 If a substance has any hazardous properties (eg, explosive, flammable, oxidizing, corrosive, toxic or ecotoxic) it is considered a hazardous substance and requires approval under the Hazardous Substances and New Organisms (HSNO) Act 1996.

Figure 1: Hazard classification used for human carcinogenicity in New Zealand.

For each hazardous substance the EPA NZ assigns a hazard classification according to its physical, health and environmental hazards. The cancer classifications used in New Zealand are coded as 6.7A (known or presumed human carcinogen) or 6.7B (suspected human carcinogen) (see Figure 1), a classification framework similar to the Globally Harmonized System of Classification and Labelling of Chemicals.

USA (EPA US)

US carcinogenicity classifications for pesticides are published by the Environmental Protection Agency’s (EPA) Office of Pesticide Programs,17 and classifications are summarised in Chemicals Evaluated for Carcinogenic Potential Annual Cancer Report.18

When assessing possible cancer risk, the EPA considers the carcinogenic potency and the potential for human exposure. The pesticides are evaluated not only to determine if they cause cancer in laboratory animals, but also as to their potential to cause cancer in humans. The factors considered include short-term studies, long-term cancer studies, mutagenicity studies and structure activity concerns. Over time, cancer classification frameworks used by the US EPA have changed as listed in Figure 2, and there is no direct correspondence between the classifications, ie, which classification is used depends on the date of the evaluation.

Figure 2: Cancer classifications used for pesticides in the US.

European Union (EU)

The hazard classifications of pesticides used as plant protection products and evaluated by the European Union are available in the EU Pesticides Database.19 The European Commission evaluates every active substance for safety before it reaches the market. Since 2007, the REACH regulation (Registration, Evaluation, Authorisation and Restriction of Chemicals) regulates the registration, evaluation and authorisation of dangerous substances and the restrictions applicable to them. The European Chemicals Agency (ECHA), established under this regulation is responsible for managing the technical, scientific and administrative aspects of REACH, and for ensuring consistency in its application

The EU uses three codes/categories to classify human carcinogenicity (see Figure 3). The EU Carcinogen 1 classification (A and B combined) is similar to the New Zealand 6.7A classification and the EU Carcinogen 2 classification to the New Zealand 6.7B classification.

Figure 3: Classifications used for human carcinogenicity in the EU.

International Agency for Research on Cancer (IARC)

The International Agency for Research on Cancer (IARC) is the specialised cancer agency of the World Health Organization (WHO). IARC’s Monographs programme on the identification of carcinogenic hazards to humans, critically reviews and evaluates the published scientific evidence on carcinogenic hazards to which humans are exposed, to provide a hazard classification. A list of classifications is available on their website.20 To date, more than 1,000 agents have been reviewed, including several pesticides. Each evaluation is carried out by a working group of independent international experts. The scientific evidence reviewed includes: (1) carcinogenicity in humans (epidemiological studies on cancer in humans exposed to the agent); (2) carcinogenicity in animals (experimental studies on cancer in laboratory animals treated with the agent); and (3) cancer mechanisms (studies of how cancer develops in response to the agent). The scientific evidence is summarised by the working group and the agent classified in one of four categories (see Figure 4).

Figure 4: Hazard classifications used for human carcinogenicity by the IARC Monograph programme.

The classification indicates the weight of the evidence as to whether an agent is capable of causing cancer (technically called “hazard”), and does not measure the likelihood that cancer will occur (technically called “risk”).21

IARC is not a regulator nor does the IARC Monographs programme recommend regulations, legislation or public health interventions, which remain the responsibility of individual governments and other international organisations.

Estimation of use of pesticides classified as suspected human carcinogens

Because the carcinogenicity categories used are somewhat different for each agency, an overarching classification of suspected carcinogenicity to humans was created for the purpose of this review, including: the EPA NZ and EU suspected group; the EPA US probable/likely/possible groups; and the IARC probable/possible groups. The active ingredients classified as suspected human carcinogens by each of the three regulators and IARC were linked to pesticide use data, to estimate the total yearly quantity of suspected carcinogens used in New Zealand agriculture. Minor use active ingredients classified as suspected carcinogens are also listed in this review, but were not included in the estimations, because data on the total weight of active ingredient used per year was not available for these.

Results

In New Zealand, more than 1,000 agrichemical products are currently licensed for use,22 with about 38 active ingredients representing >95% of the total weight of active ingredients applied. The pesticide active ingredients most commonly used in New Zealand agriculture are listed in Table 2, along with the carcinogenicity classifications of three regulatory agencies (EPA NZ, EPA US, EU) and IARC, with shaded cells representing a classification of “suspected human carcinogen” as defined in the methods section. The EPA NZ classifies five, the EU classifies eight, and the EPA US classifies 11 pesticides as suspected human carcinogens. IARC classified four as suspected human carcinogens, but most of the high-use pesticides in New Zealand have not been evaluated by IARC.

Table 2: Active ingredients with current high use in New Zealand1 and human carcinogenicity classifications by the EPA NZ, EPA US, EU and IARC.

1 Approval status: May be used as a component in a product covered by a group standard but it is not approved for use as a chemical in its own right.
2 If the substance is not classified as 6.7A or 6.7B, this is marked as (-).
3 If the substance is not classified as Carc. 1 or 2, this is marked as (-).

Figure 5 provides an overview of the percentage (on a weight basis) of active ingredients used in New Zealand classified as suspected carcinogens, using the agency-specific classifications. Using the EPA NZ classification, 3% of total weight of herbicides, 8% of fungicides and 8% of insecticides are suspected carcinogens, representing 148 tonnes of pesticides (4% of total). Using the EU classification, 10% of total weight of herbicides, 8% of fungicides and 8% of insecticides are suspected carcinogens, representing 288 tonnes of pesticides (8% of total). Using the EPA US classification, 5% of total weight of herbicides, 60% of fungicides, 8% of insecticides and 72% of plant growth regulators are suspected carcinogens, representing 872 tonnes of pesticides (26% of total). The percentage and weight of active ingredients classified as suspected carcinogens by the three regulatory agencies was highest for the fungicides (8–60%; 72–540 tonnes), followed by herbicides (3–10%; 60–200 tonnes), and insecticides (8%, 16 tonnes).

Figure 5: Pie charts of pesticide active ingredients (tonnes/year) used in New Zealand agriculture, with the outer slices representing the percentage classified as suspected carcinogens according to each respective agency’s human carcinogenicity classification.

Weight of pesticide active ingredients used yearly in New Zealand 1:

Percentage of weight of active ingredients that are classified as suspected carcinogens, according to different classifications:

These data indicate that annually New Zealand uses 148–616 tonnes of active pesticide ingredients (4–26% of total) that are classified as suspected human carcinogens, depending on which of the three regulatory agencies the estimate is based. A more sensitive classification is achieved by combining the three regulatory agencies’ classifications and also including the pesticides classified by IARC as possible or probable human carcinogens. This results in a doubling of the upper estimate to 1,730 tonnes, representing 51% of the total weight of pesticide active ingredients used in New Zealand agriculture.

Table 3 lists the active ingredients of minor use pesticides in New Zealand (ie, <1% of total), including only those that at least one of the agencies classified as a suspected human carcinogen. This indicates that an additional 11 herbicides, 15 fungicides and 14 insecticides are listed as a suspected carcinogen by at least one agency.

Table 3: Active ingredients used in New Zealand representing <1% of total active ingredients, that are evaluated as suspected carcinogen by at least one agency.

1 Approval status: May be used as a component in a product covered by a group standard but it is not approved for use as a chemical in its own right.
2 If the substance is not classified as 6.7A or 6.7B, this is marked as (-).
3 If the substance is not classified as Carc. 1 or 2, this is marked as (-).

Discussion

This review of available data on pesticide use in New Zealand and their carcinogenicity classification shows that, although no known human carcinogens are currently used as pesticides in New Zealand, a considerable number of suspected carcinogens are, representing 4–51% of the total weight of pesticide active ingredients applied.

The lowest estimate (4%) is obtained when using the EPA NZ classification, suggesting that New Zealand’s carcinogenicity classifications of pesticides are less stringent compared to other jurisdictions such as the US and the EU. Generally, resources available for chemical re-assessments in small countries such as New Zealand are limited, which may result in out of date classifications that do not incorporate the most recent evidence. Making use of the classifications and evaluations published by the EPA US and the EU, which are more regularly updated, could reduce costs and potentially risk. IARC’s hazard classifications should also be considered, as these are based on the broadest range of peer reviewed scientific data (epidemiology, animal studies and mechanistic data), and as such, more appropriately account for the multiple mechanisms through which pesticides may cause cancer; they also include epidemiological studies, where available, thus representing realistic human exposure situations. However, IARC evaluations are only available for a small number of pesticides and therefore do not provide a complete picture of the carcinogenicity of all registered pesticides, as regulatory agencies aim to do.

Pesticides recently classified by IARC as either 2A or 2B include glyphosate and 2,4-D, both widely used herbicides, and diazinon, an insecticide commonly used on pasture (to combat grass grub and porina), fruit and vegetables. Taking into account the IARC classifications for pesticides therefore greatly impacted on the here presented estimates. While only glyphosate has received considerable media attention,23 it is worth noting that glyphosate is only one in a list of 16 pesticides with high use in New Zealand that have been classified as a suspected carcinogen by at least one of the four here considered agencies.

Many of the pesticides with high use in New Zealand that are classified as suspected carcinogens are no longer approved for use in the EU, including: the herbicides isoproturon, acetochlor, alachlor, trifluralin, linuron; the fungicide tolyfluanid; the insecticides diazinon and carbaryl; and the plant growth regulator hydrogen cyanamide. This may reflect a more precautionary approach of the EU towards pesticides. Pesticide reduction programmes have resulted in substantially reduced overall pesticide use in several European countries, and this also contributes to the reduced use of suspected carcinogens. For example, in Denmark the overall pesticide use has been reported to have reduced from 4,000 to 3,000 tonnes between 1998 and 2000, while suspected carcinogenic pesticide use reduced even more, from approximately 500 tonnes (13% of total) to approximately 30 tonnes (1% of total).24 While Denmark is the only country for which such estimates could be identified from the literature, it does suggest that it is feasible, even within a relatively short time frame, to significantly reduce the use of suspected carcinogens in agriculture.

The percentage as well as weight of active ingredients classified as suspected carcinogens by the three regulatory agencies was highest for fungicides (8–60% of total fungicides weight; 72–540 tonnes), followed by herbicides (3–10%; 60-200 tonnes) and insecticides (8%, 16 tonnes). This suggests that efforts to reduce exposure to suspected carcinogens in New Zealand’s agriculture may need to focus on fungicides. Fungicides are mainly used in the horticultural sectors,1 which incidentally are also the sectors for which elevated NHL and leukemia risks have been reported in New Zealand. Despite many sustainability initiatives, the horticultural sectors continue to be the most intensive users of pesticides on a land area basis (13.2kg a.i./ha), followed by the arable (2.4kg a.i./ha), forestry (0.3kg a.i./ha), and pastoral sectors (0.2kg a.i./ha).1 New Zealand has seen an overall steady increase in pesticide use since the 1960s, with a small decline in the mid and late 1990s, likely resulting from various sustainability initiatives within the fruit sector (eg, KiwiGreen, Integrated Fruit Production).1 This was followed by a 17% increase in tonnes of total pesticide imports over the period 1999–2003,1 with herbicides increasing by 42%, fungicides by 10%, while insecticides decreased by 41%.1

A limitation of the here presented estimates is that they were based on pesticide use data published in 2005: the last date for which comprehensive data were available. Pesticide use profiles have likely changed since then, although New Zealand legislative changes for the here listed pesticides have been minor: only the fungicide benomyl, which had relatively low use in 2005, has been revoked since then, and all 16 high-use pesticides suspected to be human carcinogens have continued to be commonly used in New Zealand. The here presented estimates are therefore likely to sufficiently reflect the current use of pesticides in New Zealand. To enable assessing time-trends in the use of pesticides in New Zealand’s agriculture, including the use of suspected carcinogens, an investment will have to be made in regularly updating detailed data on pesticide use. When assessing time trends using tonnage it should be noted that newer pesticides may be active at lower doses (g per ha, rather than kg per ha for many of the older pesticides), so that a reduction in gross weight may not necessarily equate to reductions in risks to health.

In summary, this review indicates that a large volume of pesticides used in New Zealand are suspected carcinogens. As a result, we will likely continue to see an increased risk of cancer, in particular leukaemias and lymphomas, for people who frequently use pesticides as part of their work. A pesticide risk reduction programme, as has successfully been implemented in several other countries (eg, Denmark), will likely reduce this risk, while also reducing the risk of several other health effects associated with pesticides (eg, impaired neurobehavioral function, neurodegenerative diseases, impaired fertility). In the absence of this, pesticide risk reduction will continue to depend largely on voluntary action by its users, which is unlikely to be sufficiently effective. Efforts to reduce the health risks of pesticides require government leadership, through for example the Ministry of Health’s National Cancer Action Plan, WorkSafe’s Strategic Plan for Work-Related Health, and NZ EPA’s regulation of pesticides. Medical professionals may also play a role by: (1) considering patients’ occupations and associated hazardous exposures; (2) communicating potential risks associated with pesticides to patients and the general public; and (3) promoting and supporting patients’ efforts to reduce pesticide exposure to themselves and their families.

Summary

Abstract

Aim

To estimate the number and weight of pesticides used in New Zealand agriculture that are classified as known or suspected human carcinogens.

Method

The yearly usage of active ingredients was extracted from the most recent (2005) report on pesticide use. For each active ingredient, the carcinogenicity classification of three regulatory agencies (New Zealand Environmental Protection Authority [EPA NZ], US Environmental Protection Agency, European Chemicals Agency) was extracted. The International Agency for Research on Cancer (IARC) Monograph Programme’s classifications were also considered. Total tonnes of active ingredients were calculated according to each classification.

Results

None of the pesticides are classified as known human carcinogens. In total, 56 active ingredients are listed as suspected carcinogens by at least one of the four agencies, including 16 high-use ingredients, representing up to 51% of the total yearly quantity. Agency-specific estimates ranged between 4–26% (148–872 tonnes) with the EPA NZ classification yielding the lowest estimate. The suspected carcinogen weight was highest for fungicides (estimates based on the three regulatory agencies ranged between 72–540 tonnes), followed by herbicides (60–200 tonnes) and insecticides (16 tonnes).

Conclusion

New Zealand’s use of pesticides that are suspected carcinogens is high. Efforts to increase awareness and reduce exposure need to be considered.

Author Information

Andrea Martine 't Mannetje, Centre for Public Health Research, Massey University, Wellington.

Acknowledgements

Correspondence

Dr Andrea Martine 't Mannetje, Centre for Public Health Research, Massey University, Wellington 6140.

Correspondence Email

a.mannetje@massey.ac.nz

Competing Interests

Nil.

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