![]() ![]() The neurotoxic signs were reversible and were at doses that exceeded general toxicity. Neurotoxicity studies showed aberrations in locomotion and open feld behavior at high doses saturating renal clearance but no histopathological findings in neural tissues. Experimental in vitro and in vivo animal studies show no genotoxic potential for 2,4-D. Reduced bodyweight gain has been seen at the higher doses (generally above the level at which renal excretion is saturated), with reduced food intake usually seen in parallel. In two-generation reproduction studies there were no effects seen on fertility indices at doses up to and including 72 mg/kg/day. Studies in both rats and mice have shown no carcinogenic effect of 2,4-D and the US EPA classifes 2,4-D as a Group D chemical (not classifable as to human carcino-genicity). Chronic toxicity of 2,4-D has been tested in laboratory animals at a wide range of dose levels ( Garabrant & Philbert, 2002 EPA, 2005). Toxicity observed in rodents at doses above renal saturation is generally not regarded as relevant to human health risk ( Timchalk, 2004 EPA, 2005). 2,4-D is cleared into urine of both animals and humans by a saturable organic anion transporter, OAT-1 toxicity of 2,4-D in rodents is typically limited to dose levels that saturate renal clearance (>50 mg/kg/day). In humans, 2,4-D is excreted unmetabolized in urine with a half-life of 10 to 33 hours, an average of 17.7 hours ( CDC, 2009 Sauerhof et al., 1977). In aerobic environments, 2,4-D degrades rapidly from 2 to 13 days ( Wilson et al., 1997). As a selective herbicide, 2,4-D is used to control broadleaf weeds in a variety of settings from crops, rights-of-way, lawns, forests to aquatic settings. The herbicide, 2,4-D, has been registered for use since the 1940s. ” Since no qualitative review of the 2,4-D epidemiology literature since 2001 has been published we present an update in this paper. Reviewing the literature through 2001, Garabrant and Philbert (2002) observed more strongly that the epidemiology data “provide scant evidence that supports a conclusion that exposure to 2,4-D is associated with STS, NHL or HD. (2000) emphasized the inconsistent nature of the studies up to 2000 that precluded drawing any conclusion on carcinogenicity in humans. Recently re-registered for use by Health Canada (2008), and the US Environmental Protection Agency, EPA (2005), 2,4-D is currently being re-evaluated by the European Union. ![]() ![]() The herbicide, 2,4-dichlorophenoxyacetic acid (2,4-D), is an example of a pesticide for which the epidemiology data are continually reviewed and debated. For this reason and for public health purposes, in general, a critical review of the epidemiologic literature on crop protection products is of increasing value. While most regulatory agencies heavily rely on toxicological data, the results of epidemiology studies are becoming more and more important in this area. In the context of biomonitoring, the epidemiology data give no convincing or consistent evidence for any chronic adverse effect of 2,4-D in humans. However, most lack precision and the results are not replicated in other independent studies. In general, a few publications have reported statistically significant associations. The 2,4-D epidemiology literature after 2001 is broad and includes studies of cancer, reproductive toxicity, genotoxicity, and neurotoxicity. Information from biomonitoring studies increases our understanding of the validity of the exposure estimates used in epidemiology studies. Occupational exposure, where exposure was highest, was positively correlated with behaviors related to the mixing, loading and applying process and use of personal protection. bystanders, the urinary 2,4-D levels were also very low except in individuals with opportunity for direct contact with the herbicide. Among individuals with indirect exposure, i.e. In the general population, 2,4-D exposure is at or near the level of detection (LOD). In order to compare the exposure of the general population, bystanders and occupational groups, their urinary levels were also reviewed. A qualitative review of the epidemiological literature on the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) and health after 2001 is presented. ![]()
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