Impurities in Agricultural Chemicals
Last updated 12 April 2010
Why are there impurities in agricultural chemicals?
Agricultural chemicals can contain impurities as by-products of the manufacturing process. These impurities are identified as part of the registration process when pesticide manufacturers are required to provide detailed chemistry and manufacturing information to the APVMA.
Impurities that are reported are then assessed to determine if they present any risks to human health and/or the environment. Standards, based on toxicological testing, define the maximum allowable level of specific impurities for each active constituent.
How can the APVMA allow pesticides to be sold when they have dioxins in them?
Dioxins are formed through natural and industrial combustion processes. They can also be formed as unintended by-products of the manufacturing processes for certain types of chemicals. They may appear in some pesticides at trace levels. With improvements to manufacturing and analytical technology, it has become possible to better manage production processes to keep dioxins contamination below levels of concern.
Generally, it has been considered that the contribution that modern pesticides make to background dioxin emissions to the environment is very small. They were not considered, for example, as a potential source in the 2004 report Inventory of Dioxin Emissions in Australia, conducted for the Department of the Environment, Water, Heritage and the Arts, which identified a range of natural and industrial processes as major contributors to dioxin levels in Australia (see below under ‘How are they produced and what are the major sources?’).
How long has the APVMA known these particular impurities exist?
Quintozene was approved prior to the formation of the APVMA and its predecessor, the National Registration Authority. It was only in June 2009 that the APVMA received information that some quintozene products may contain dioxins at levels sufficiently high to be of possible human health concern. The APVMA then tested a number of samples of registered quintozene products to investigate the extent of the problem.
Do other pesticides on the Australian market also contain dioxins?
Some other pesticides may contain dioxins but not at levels likely to raise human health concerns. Recent analysis indicates that dioxin levels in a number of approved pesticides that were tested are in the order of 20 to 1000 times lower than those found for quintozene.