Atrazine chemical review

In December 1995, the APVMA (formerly the NRA) began a review of atrazine as part of the Existing Chemical Review Program, which was established to systematically review a number of agvet chemicals that had been on the Australian market for some time.

Atrazine was nominated for review because of concerns over possible links to cancer, its potential to contaminate groundwater and surface water, lack of maximum residue limits (MRLs) for major commodities, and a reported lack of efficacy for some uses.

Interim review report

In November 1997, the APVMA released the Atrazine interim review report. The report found that there were no major toxicological concerns with atrazine’s active constituent and that the use of atrazine products posed no undue hazard to most users. New conditions for the use of atrazine were implemented to reduce chemical handling by workers and to reduce drift and run-off into water bodies. The changes included:

• the cancellation of industrial and non-agricultural uses of atrazine, including home-garden uses (cancellation of sale and supply of these atrazine products took effect from 31 December 1998; the application of existing stocks was allowed to continue until 30 June 1999)
• the inclusion of more extensive safety instructions on product labels to reduce chemical handling by workers, spray drift and run-off into water bodies
• the deletion of MRLs for commodities for which there were no current use patterns (citrus, grapes and pineapples).

The APVMA found that additional environmental and residue information was required, and registrants were given up to three years to generate these data. Assessment of the data led to the development and publication of a draft final report.

At the same time as the interim review was released, restrictions on the use of atrazine were introduced in response to detections of atrazine in water bodies and to minimise any further potential risks to the environment. The restrictions were:

• no mixing/loading or application within 20 metres of any well, sinkhole or intermittent or perennial stream
• no application within 60 metres of natural or impounded lakes or dams
• no use in channels and drains
• a maximum annual rate of application of 3 kilograms active ingredient per hectare (kg ai/ha) in all crops except plantation forestry (in which the maximum rates are limited to 4.5 kg ai/ha per year in sandy soils and soils defined as ‘highly erodible’, and 8 kg ai/ha per year in clay loams and heavier textured soils).

These restrictions remain in force.

Draft final review report

In April 2002, the APVMA released the Atrazine draft final review report for public comment. At that time, a number of newly published overseas studies raised additional concerns that atrazine might cause developmental and reproductive problems in frogs. Because of those concerns, the APVMA delayed finalisation of the review in order to investigate the claims and reassess the toxicological and environmental risks of using atrazine.

Second draft final review report

In October 2004, the APVMA released the Atrazine second draft final review report. The report considered all regulatory action taken since the release of the 1997 interim report recommendations, new residues and environmental data, and assessments of the United States EPA frog studies.

The APVMA found that atrazine was unlikely to have an adverse impact on amphibians at existing levels of exposure. However, it concluded that the issue of atrazine and amphibians should be revisited if additional data demonstrated that atrazine posed a hazard to frog populations at realistic levels of exposure.

The APVMA also found that atrazine does not pose a risk to human health, but that the use of products containing atrazine in non-agricultural situations might pose a risk to the environment. Changing the use instructions on product labels would reduce or eliminate those risks.

The APVMA was satisfied that varying product labels and approvals would ensure that atrazine products would continue to meet the requirements for continued registration and use in Australia.

In the 2004 report, the APVMA proposed amending product labels to include:

• a larger buffer zone and additional precautionary statements
• a new withholding period of 28 days for grazing on all crops except canola
• details for reporting incidents of herbicide resistance or breakdowns in efficacy.

In the final report of March 2008, the APVMA affirmed the active constituent and required registrants to amend label instructions for newly manufactured stocks of products containing atrazine to reflect the outcomes of the review. Most of the regulatory actions detailed in the final report were proposed in the 2004 report. They included amended label instructions intended to further reduce the risk of atrazine entering waterways, updated information on withholding periods and additional information on weed resistance reporting.

In May 2008, the APVMA varied the label instructions for the use of atrazine products. Specifically, these changes were to further reduce the risk of atrazine entering waterways, update the information on withholding periods and additional information on weed resistance reporting. This followed the regulatory actions taken in 1997, which resulted in cancellation of industrial, home garden, commercial turf and non-agricultural uses of atrazine; and introduction of buffer zones around waterways or water sources, removal of uses in channels or drains and limits on the application rates to reduce the risk of atrazine entering waterways. Once these changes were made the APVMA was satisfied that the continued use of atrazine products met the safety, efficacy and trade criteria for continued use.

The phase out period for the use of the older labels was completed by May 2010.

After the completion of the review in June 2010, the APVMA published an assessment of further information about the toxicity of atrazine and potential modes of action of this toxicity. This assessment concluded that a re-evaluation of the existing health values was not required.

To access full copies of all reports, media releases and gazette notices for the reconsideration of atrazine click on the Publication Archive heading below on the left.