Age article resurrects simazine controversy

The Age newspaper has run an article about the dangers of simazine, which is present in some swimming pool algaecides. The Age article was prompted by a Friends of the Earth media campaign aimed at removing simazine products from the Australian market.

Simazine is a triazine, along with atrazine and cyanazine. It had been linked to tumours in test rats, resulting in the Environmental Protection Agency (EPA) in the US reviewing the use of the chemical in 1994. Following the review, it was banned in 1996. The EPA has since revised that ruling and allowed companies to apply for registration. Meanwhile, its use been restricted in Europe.

The chemical is most commonly used as an agricultural herbicide and pesticide. The main problem overseas seems to have been that simazine residue may enter groundwater, and may then take some time to clear.

Paul Simons, director of chemical manufacturer Lo-Chlor, manufacturer of non-simazine algaecides, says he has been trying to educate the industry for years about the potential risks from simazine. This included an informational seminar he gave at a SPASA NSW trade day. He believes if simazine has run into trouble in Europe and the US, there must be compelling evidence, and it also should be removed from Australian pools.

Wobelea director William Bliss, supplier of Poolkare products including Zed Zed 60 algaecide, disagrees that simazine-based products are dangerous in the swimming pool environment. For a start, he says that the Poolkare product, Zed Zed 60, is not recommended for use in indoor pools or heated pools, and is mainly used to winterize outdoor pools. It was the first simazine based pool algaecide registered for use in Australia more than 30 years ago.

Bliss says that because simazine was developed originally for weed control and is still used for that purpose, two misconceptions arose. The first is that it kills grass and plants around the pool, however the concentration of simazine in the pool is 100-times less than required for weed control. The second is that it is toxic to humans and animals. Bliss says that simazine is exempted from listing in the Standard for Uniform Scheduling of Drugs and Poisons due to its low toxicity. In fact, he says its toxicity ratings for mammals (including humans) by oral or dermal rates are less than for common salt. It is practically non-toxic to birds and exhibits very minor toxicity to fish.

He says the LD50 (or median lethal dose) is greater than 10,000 mg/kg (rat). Zed Zed 60 is 60 mg/L active. This means that an adult weighing 80kg would need to swallow in excess of 13 litres of Zed Zed 60 to achieve a near fatal dose. Diluted in the pool, it is even less dangerous says Bliss, adding that a typical seven- or eight-year-old weighing 20kg would need to drink 200,000L of pool water to ingest a near fatal dose of simazine.

Paul Simons agrees that simazine diluted in a pool may in fact have a very low toxicity, but he is also concerned about people who have to handle it before it is put in the pool.

While simazine and atrazine were banned in the US in 1996, the EPA has since revisited the situation, and has now stated the chemicals are below the agency’s level of concern. Atrazine and simazine have been reclassified as “not likely to be carcinogenic to humans.” The Agency determined that, with label amendments and other specific changes, there is a reasonable certainty that no harm will result to the general US population, infants, children, or other major identifiable subgroups of consumers, from the use of simazine. As such, US manufacturers have become eligible to apply for re-registration with new labelling.

However, simazine based products are still not used in the US pool industry, and have not been for many years. According to US pool chemical expert Tom Lachocki, the US industry has managed – and continues to manage – perfectly well without them. You can go to the EPA’s 2006 document on the re-registration decision here.