Let's throw caution to the wind ... but at what cost?

In 2004 the European Union withdrew its approval for atrazine, a herbicide produced by Syngenta, a Swiss based agrochemicals multinational, because of its persistent groundwater contamination. The chemical has long been under fire for potentially more sinister side effects: for example, its use has long been controversial because of its effects on non-target species like frogs  and a lot of scientific studies (see here and here) have raised questions about whether atrazine may cause a variety of cancers and harm human and animal reproductive and hormone systems.

Tyrone Hayes, a biologist at University of California, Berkeley, has a web page about his research on the chemical.

The European Union generally takes the sensible approach of dealing with potential dangers on the "precautionary principle" principle, but the "precautionary principle" doesn't operate in the United States or back home in Australia where atrazine continues to be used to control grass and weeds in crops like sorghum, maize, sugar cane, lupins, pine and eucalypt plantations and triazine-tolerant canola.

In July 2007 the Australian National Health and Medical Research Council announced a review of its guidelines on atrazine in drinking water. It plans to report by the end of 2009. We wait with bated breath!

Last year there was a review of atrazine use by our government watchdog, the Australian Pesticides and Veterinary Medicines Authority (APVMA), as a result of concerns raised over human and animal carcinogenicity, environmental impacts including the potential for contamination of ground and surface water, and residue and efficacy uncertainties. Australian farmers were delighted with the authority's decision to allow the continued use of the herbicide, despite international debate over its health and environmental effects.

At the time it was reported that the APVMA's Dr Simon Cubit defended the review, saying it relied on a database of thousands of scientific papers as evidence. He could not say how many studies in the database were Australian, but said the data was extensive enough to reflect the risk of atrazine in the Australian environment. "At present we don't believe it's a significant issue," he said. Cubit also said, and still says, that the APVMA will re-open the atrazine review if new credible evidence of impact emerges.

Well, the April 2009 issue of the medical journal Acta Pædiatrica reported that birth defect rates in the United States were highest for women conceiving in the spring and summer, a period of increased risk which correlated with increased levels of pesticides in surface water across the United States. Studying all 30.1 million births which occurred in the U.S. between 1996 and 2002, the researchers found a strong association between the increased number of birth defects in children of women whose last menstrual period occurred in April, May, June or July and elevated levels of nitrates, atrazine and other pesticides in surface water during the same months. As far as I know this is the first study to link increased seasonal pesticide concentration in surface water with the peak in birth defects in infants conceived in the same months.

And earlier this year the Reef and Rainforest Research Centre published a Water Quality Research Report raising concerns about risks to the Great Barrier Reef and to human health.from chemicals including atrazine. What stance does our watchdog take when concerns like this are raised? Defensiveness, pure and simple.

APVMA responded by saying its March 2008 review of atrazine "... considered claims of carcinogenicity and endocrine disruption. Based on evidence currently at hand the international scientific consensus is that there is no evidence that atrazine causes cancer in humans. Likewise, claims of endocrine disruption on mammals at very low levels are not currently supported." Media Release - Chemical Concerns on Human Health and Reef Overstated (PDF 30KB)

It then reassures us with the usual: "The APVMA will continue to work with Commonwealth and Queensland authorities and play its role in ensuring that regulation of agricultural chemicals is appropriate and that the Reef and the community is protected. The APVMA will monitor any new research that emerges in relation to atrazine and other agricultural chemicals and will act quickly if risks are identified."

Even scientific studies have limitations. A good example is a recent study of long-term low-level atrazine exposure in rats which yielded opposite results to earlier studies of the effects of acute exposure to high concentrations.

But the problem for us is that APVMA doesn't do its own independent research - which, obviously, it couldn't feasibly do - so it monitors developments and reviews scientific studies.