Effectiveness of Integrated Best Management Practices on Mitigation of Atrazine and Metolachlor in an Agricultural Lake Watershed

The study examined the influence of land-use (cropping patterns) and integrated agricultural best management practices (BMPs) on spring herbicide levels in an agricultural watershed. Atrazine and metolachlor were applied for weed control during spring of 1998-2002, 2005, and 2007-2013. Watershed-wide mass of applied herbicides ranged from 12.7 to 209.2 g atrazine and 10.9-302.2 g metolachlor with greatest application during 1998, 2009-2010 (atrazine) and 2007-2013 (metolachlor). Spring herbicide concentrations in Beasley Lake water ranged from below detection to 3.54 μg atrazine/L and 3.01 μg metolachlor/L. Multiple linear regression analyses with cropping patterns, BMPs, rainfall and time as independent variables, showed atrazine applications were associated with increases in cotton acreage and quail buffer, while metolachlor applications increased over time. Multiple linear regressions showed lake atrazine concentrations were associated with conservation tillage, rainfall, and corn, while lake metolachlor concentrations were associated with the cumulative metolachlor application and sediment retention pond installation.

Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in human milk samples collected across Canada in 1986-87

Monitoring of human milk samples for the presence of chemical contaminants has been carried out in Canada for several decades. In 1986-87 over 400 donations of human milk were collected nationwide and 100 of these, selected by province according to population, were analysed for the PCDDs/PCDFs. The results show the presence of about eleven different analytes all with 2,3,7,8-substitution with the PCDDs at higher and more variable concentrations than the PCDFs. On a 2,3,7,8-TCDD toxic equivalents (TEQ) basis, the mean value for the country is about 15 ng per kg milk fat. This TEQ value is similar to that from many other industrialized nations and about 50% lower than certain European states. Little or no variation was apparent in the milk content among the various Canadian provinces probably reflecting the uniformity of the general food supply across the country. Limited data over a period of five years suggest the average level of these compounds in human milk may be decreasing.

Study of chlorinated diphenyl ethers and chlorinated 2-phenoxyphenols as interferences in the determination of chlorinated dibenzo-p-dioxins and chlorinated dibenzo furans in biological samples

Two classes of environmentally occurring chlorinated aromatic hydrocarbons which have mass spectral properties similar to the chlorinated dibenzo-p-dioxins (dioxins) and chlorinated dibenzofurans (furans) were studied. Standards of chlorinated diphenyl ethers (CDEs), and chlorinated 2-phenoxyphenols (CPPs) and their methyl ethers, along with the dioxins and furans were passed in steps through a simple method for the analysis of the latter compounds in biological samples. The CDEs, which interfere with the determination of furans by mass spectrometry, had similar extraction, high-performance liquid chromatographic and gas chromatographic properties as the furans but, in all cases studied, were well separated from them on an activated Florisil column using combinations of hexane and dichloromethane as eluting solvents. The higher CPPs on the other hand tended to generate dioxin residues by ring closure when exposed to strong hydrochloric acid solution during sample preparation. In addition, their methyl ethers containing four to six chlorines tracked completely through all stages of the method with the dioxins. Thus, if the methyl ethers of CPPs were present in a sample extract, additional mass spectral information would be needed to further differentiate them from dioxins in environmental samples.

In vivo and in vitro binding of alpha- and gamma-hexachlorocyclohexane to mouse liver macromolecules

alpha-Hexachlorocyclohexane (alpha-HCH) but not gamma-HCH, produces a strong neoplastic response in HPB strain mouse liver. In vivo and in vitro binding studies with 14C-labelled HCH isomers showed no preferential binding of the alpha-HCH isomer to protein or DNA. Moreover, the binding of both isomers to DNA in vivo or in vitro occurred only at very low levels, a result consistent with the lack of mutagenic activity associated with these compounds. The results suggest that the neoplastic response observed with alpha-HCH results from a non-genotoxic mechanism.