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Identifying dangerous pesticides

17 September 2010
Last updated 20 September 2010

Recently WWF Australia commissioned the National Toxics Network, ‘a community-based network working for a toxic-free future’, to develop ‘a list of the most dangerous pesticides registered in Australia (external site)’.

What did they come up with and how does it compare with other lists that seek to identify chemicals that are either dangerous or of particular concern?

NTN lists just over 120 active constituents that were approved in Australia as of July 2010. The criteria used to select these chemicals as ‘dangerous’ were those:

  • prohibited in the European Union
  • the World Health Organization (WHO) had identified as hazardous to varying degrees
  • flagged by various regulatory authorities as a potential carcinogen
  • flagged by various regulatory authorities as a endocrine disruptor.

Are these criteria effective measures of what might constitute a dangerous chemical? Some may be, but generally they are not. Let’s look at them in a bit more detail.

Prohibited in the EU

Some 80 active constituents were listed as prohibited in the European Union. These, NTN/WWF claim in a media statement, were prohibited ‘because of the risks they pose to human health and the environment.’

This claim is incorrect on two levels. Firstly, NTN has misrepresented the outcomes of recent EU review processes. Taking the recently completed major EU review of plant protection chemicals as an example, 67% of active constituents that were in use when the review commenced were never formally assessed for human health or environmental issues. They were withdrawn from the review by manufacturers before the assessment stage. Commercial considerations were a dominant reason for this withdrawal. To support their chemicals through the review process manufacturers would have been required to spend millions of dollars to generate new scientific data. In many cases the commercial return from sales of these chemicals was insufficient to support this investment.  Many chose simply to withdraw from the process. Some 34% did go through to assessment with 70 (7% of the total number) failing that assessment on health or environmental grounds.

What NTN/WWF has done is to lump together those that were withdrawn from the assessment and those that failed the assessment and claim they were all prohibited because of human health and environmental concerns. This is obviously not true so, to this extent, suggesting that lack of European approval is a way of identifying dangerous chemicals is seriously flawed.

The argument fails at a more fundamental level however. Many of the chemicals NTN/WWF claim to be prohibited in Europe continue to be used in many European countries under exemption provisions. Considering plant protection chemicals alone, some 25% of the 80 are authorised for use in one or more different European countries.

Perhaps more significantly, many of the 80 identified chemicals are widely used throughout the world in countries with well-developed regulatory systems such as Canada, the United States, New Zealand and South Africa.

It is also important to note that the European Union has approved active constituents that are not permitted in Australia.

On this basis, the criteria of the lack of approval of an active constituent in Europe does not provide any meaningful basis for defining a dangerous chemical. 

Hazardous chemicals

The next criterion NTN has chosen to define a dangerous chemical are those defined by the World Health Organization as presenting significant hazards.

There is some merit in this criterion. Within Australia, for example, all drugs and poisons are scheduled by the National Drugs and Poisons Scheduling Committee. One schedule maintained by the Committee, Schedule 7, is labelled ‘Dangerous Poison’. This schedule is for substances with a high potential for causing harm at low exposure and which require special precautions during manufacture, handling or use.

While this labelling flags a hazard, in much the same way as World Health Organization hazard classifications do, these chemicals are only dangerous if people are exposed to them at harmful levels. If regulators choose to register products containing these chemicals they must be satisfied that sufficient controls are in place to limit exposures to safe levels. These controls are far reaching. Schedule 7 substances are only available to specialised authorised users who have the skills necessary to handle them safely. Special conditions restricting their possession, storage and use also apply.

Thus while hazard classifications have some value in flagging danger, this value lies only in identifying potential hazards. Generally speaking, provided label instructions are followed and the user has the necessary training, products with hazardous active constituents can be used safely.

It is interesting to note that there are nearly 200 substances currently listed as dangerous poisons by the National Drugs and Poisons Scheduling Committee. The NTN/WWF list contains less than thirty of them.  

Potential carcinogen and endocrine disruptors

The potential of a chemical to promote cancer in humans or to be an endocrine disruptor are discussed together here as both are specific examples of a chemical hazard. The key concept, as discussed previously, is that of exposure. Chemicals may produce these effects if people are exposed to them at harmful levels. Regulators take these risks very seriously. They assess large amounts of data and will generally only approve uses of formulated products if safe exposure thresholds can be clearly established.

To this extent the classification of a chemical as a potential carcinogen or endocrine disruptor is not an accurate measure of its danger to end users. The approved uses of a chemical product, when used according to label instructions, may present none of these dangers.

Chemicals of concern

So if the WWF/NTN criteria have limited value in identifying dangerous chemicals what are useful measures? How do we determine chemicals that present actual rather than potential risks to human health or the environment? 

There are a number of processes that are typically used. At a national level, the APVMA works closely with user groups, state and territory authorities, health and environmental experts and the scientific community to identify issues with currently registered pesticides and veterinary medicines that are used according to label instructions. These issues can potentially emerge from many sources. New scientific information for example, might reveal that the controls imposed on a chemical are inadequate. Research might suggest, for example, that the threshold levels were set too low. It might indicate that the chemical may act on the human body in a way not previously understood or that it behaves in the environment differently than expected. Each constitutes a potential risk.

The APVMA, like most regulators, maintains a list of these chemicals. Once identified, they are reviewed. In most cases, the outcome of these reviews is to tighten controls. Less frequently, the chemicals are removed from the market. Around forty are currently under review, with another thirty allocated to four prioritised lists. The issue to be reviewed is also listed. Currently less than a third of chemicals on the NTN/WWF list appear on the APVMA review list.

At an international level there are also processes that seek to identify chemicals that present specific (often cross-jurisdictional) risks. The Stockholm Convention on Persistent Organic Pollutants is one such example. Australia is a signatory to this treaty and may withdraw chemicals listed under the Convention from the Australian market following a whole of government consideration and ratification process. Recently, for example, the APVMA de-registered lindane after it has been listed under the Convention because the sole registrant voluntarily withdrew its registration. The WWF/NTN list identifies a handful of chemicals listed under various treaties on which Australia is a signatory. Australia is compliant with its obligations under all these treaties.

How effective is the NTN/WWF list in identifying the most dangerous pesticides registered in Australia?

In conclusion, the criteria used by the NTN to identify dangerous pesticides have limited value. Chemicals approved in one country but not another is very rarely a useful measure of danger given differences in legislation, climate, cultural practices and use patterns. Similarly, proposing hazard as a criteria ultimately has limited value in the sense that it is not a real measure of the exposure people actually experience. While NTN has identified some chemicals that national and international regulatory authorities would regard as possessing specific potential risks, the majority are widely used around the world and, on current information, are not the subject of specific regulatory concern.

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Last updated on 19 January, 2012