Pesticide residues in food — 2007: Toxicological ... - ipcs inchem

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in the early 1990s; this reflects restrictions on the use of atrazine that were introduced in the late
1990s and early 2000s and the introduction of the “Good Farming Practice Programme” (GFPP) in
the European Union (EU) and other parts of the world and “Best Management Practices” (BMPs)
in the USA. Therefore, older monitoring data generally represent an overestimate of environmental
concentrations likely to arise from current use practices. In surface water, the concentrations of the
chlorotriazine metabolites of atrazine are generally less than those of atrazine itself, while the concentrations
of these metabolites in rural wells are more similar to those of atrazine.
Consideration of data from monitoring carried out in a number of countries indicate that concentrations
of atrazine and its chloro-s-metabolites in groundwater and surface water rarely exceed
the current WHO guideline value of 2 ppb; levels are commonly well below the EU “parametric
value” for pesticide residues in drinking-water of 0.1 ppb. Specific monitoring of drinking-water
indicates that:
• recent data from the USA show that in no public-water supplies does the concentration of atrazine
exceed the United States Environmental Protection Agency (EPA) Drinking Water Levels of
Comparison (DWLOCs) for any age group;
• concentrations of atrazine in the United Kingdom (UK) are less than 0.1 ppb; and
• in Canada, concentrations are lower than in “raw” groundwater or surface water.
Hydroxyatrazine is a plant metabolite of atrazine. It can also be formed in acidic and humitic
soils. It is reported to bind to soil to a greater extent than parent atrazine or the chlorinated metabolites.
Hydroxyatrazine has been less frequently measured in monitoring programmes than parent
atrazine or the chlorinated metabolites; however, in studies in which hydroxyatrazine has been measured,
it was generally detected less frequently than were the chlorinated metabolites, and commonly
at lower concentrations. The available data suggest that hydroxy compounds are unlikely to significantly
contaminate surface water.
Evaluation for acceptable daily intake
Unless otherwise stated, the studies evaluated in this monograph were performed by laboratories
that were certified for GLP and that complied with the relevant Organisation for Economic
Co-operation and Development (OECD) test guidelines or similar guidelines of the EU or United
States Environmental Protection Agency. As these guidelines specify the clinical pathology tests normally
performed and the tissues normally examined, only significant exceptions to these guidelines
are reported here, to avoid repetitive listing of study parameters.
1. Biochemical aspects
1.1 Absorption, distribution and excretion
Rats
In a study on absorption, distribution and elimination, male Sprague-Dawley rats received daily
oral doses of [ 14 C]atrazine ([U 14 C]-triazine labelled; radiochemical purity, ≥ 97.5%) for up to 7 days
at 0.1 mg per rat (equal to approximately 0.4 mg/kg bw) or 1.0 mg per rat (equal to approximately
4.0 mg/kg bw). Groups of three rats were killed 5, 7, 9, 10, 14 and 18 days after the start of dosing,
and blood and tissues were sampled for radioactivity. From the rats killed after 18 days (11 days after
last dose), faeces and urine were collected for periods of 24 h; tissues were analysed for radioactivity,
and a final material balance was calculated. A material balance of 103.9% and 93.4% was achieved for
the doses at 0.4 and 4.0 mg/kg bw, respectively. Recovery of radiolabel was approximately 67–73% in
ATRAZINE 37–138 JMPR 2007