Risk Assessment of Glyphosate Exposures from Pilot Study with Simulated Heavy Residential Consumer Application of Roundup® using a Margin of Safety (MOS) Approach.

Due to the widespread application of glyphosate, a nonselective herbicide, to a variety of resistant food crops, the general population is exposed to glyphosate through dietary intake. Despite this, dietary exposures to glyphosate are considered low in comparison to application-related exposures. Although previous studies have evaluated exposure to horticultural and agricultural workers, to date only one study, which we recently conducted, has characterized exposure to glyphosate in consumers following heavy residential application of a glyphosate-containing herbicide in a residential yard and garden setting. In this previous study, we demonstrated that urinary glyphosate concentrations in these applicators were similar to or in some circumstances greater than those in occupational applicators, likely due to the nature of the simulation study, which ensured a heavy application protocol. However, it is unknown whether these urinary glyphosate concentrations in consumer applicators correspond to internal doses that may be of concern. Therefore, the purpose of this study is to provide a comprehensive risk assessment of glyphosate exposure in consumer applicators using a margin of safety approach. Here, we incorporated data collected from multiple spot urine samples across time from our previous study that assessed consumer exposure to glyphosate from Roundup® application. Estimated internal doses, even with the use of conservative assumptions across unique approaches, were below internal doses estimated from established health-based guidance values. Overall, this study demonstrates that glyphosate exposure from even heavy consumer application of a commercially available glyphosate-containing herbicide does not appear to be a health concern.

Survey of 24-h personal formaldehyde exposures in geographically distributed urban office workers in the USA.

An air sampling study was conducted to evaluate personal formaldehyde exposures in a group of office workers spread across five geographical locations in the USA. Passive badge samples for formaldehyde were collected on three participants in each location, as well as in the office and home indoor microenvironments of each participant over 3 individual days. Median personal 24-h formaldehyde concentrations ranged from 9.9 to 18 µg/m3. Personal 24-h formaldehyde concentrations in one location were significantly higher than concentrations measured in the other four locations; no significant differences existed between any of the other locations. The participants in this study spent an average of 53% of their daily time in their homes, 36% at their office, and 11% in other indoor and outdoor locations. A comparison of measured 24-h personal formaldehyde concentrations and a model of average exposure based upon measured concentrations in the indoor microenvironments suggested that both the home and office formaldehyde concentrations were a strong predictor (R2 = 0.88) of overall personal exposure. The data from this study are representative of office workers in urban environments and can be used as background formaldehyde exposure levels (in the absence of specific sources) for both occupational and nonoccupational exposure assessments.

Residential metal contamination and potential health risks of exposure in adobe brick houses in Potosí, Bolivia.

Potosí, Bolivia, is the site of centuries of historic and present-day mining of the Cerro Rico, a mountain known for its rich polymetallic deposits, and was the site of large-scale Colonial era silver refining operations. In this study, the concentrations of several metal and metalloid elements were quantified in adobe brick, dirt floor, and surface dust samples from 49 houses in Potosí. Median concentrations of total mercury (Hg), lead (Pb), and arsenic (As) were significantly greater than concentrations measured in Sucre, Bolivia, a non-mining town, and exceeded US-based soil screening levels. Adobe brick samples were further analyzed for bioaccessible concentrations of trace elements using a simulated gastric fluid (GF) extraction. Median GF extractable concentrations of Hg, As, and Pb were 0.085, 13.9, and 32.2% of the total element concentration, respectively. Total and GF extractable concentrations of Hg, As, and Pb were used to estimate exposure and potential health risks to children following incidental ingestion of adobe brick particles. Risks were assessed using a range of potential ingestion rates (50-1000mg/day). Overall, the results of the risk assessment show that the majority of households sampled contained concentrations of bioaccessible Pb and As, but not Hg, that represent a potential health risk. Even at the lowest ingestion rate considered, the majority of households exceeded the risk threshold for Pb, indicating that the concentrations of this metal are of particular concern. To our knowledge, this is the first study to quantify key trace elements in building materials in adobe brick houses and the results indicate that these houses are a potential source of exposure to metals and metalloids in South American mining communities. Additional studies are needed to fully characterize personal exposure and to understand potential adverse health outcomes within the community.

Contrasting effects of chloride on growth, reproduction, and toxicant sensitivity in two genetically distinct strains of Hyalella azteca.

The strain of Hyalella azteca (Saussure: Amphipoda) commonly used for aquatic toxicity testing in the United States has been shown to perform poorly in some standardized reconstituted waters frequently used for other test species. In 10-d and 42-d experiments, the growth and reproduction of the US laboratory strain of H. azteca was shown to vary strongly with chloride concentration in the test water, with declining performance observed below 15 mg/L to 20 mg/L. In contrast to the chloride-dependent performance of the US laboratory strain of H. azteca, growth of a genetically distinct strain of H. azteca obtained from an Environment Canada laboratory in Burlington, Ontario, Canada, was not influenced by chloride concentration. In acute toxicity tests with the US laboratory strain of H. azteca, the acute toxicity of sodium nitrate increased with decreasing chloride in a pattern similar not only to that observed for control growth, but also to previous acute toxicity testing with sodium sulfate. Subsequent testing with the Burlington strain showed no significant relationship between chloride concentration and the acute toxicity of sodium nitrate or sodium sulfate. These findings suggest that the chloride-dependent toxicity shown for the US laboratory strain may be an unusual feature of that strain and perhaps not broadly representative of aquatic organisms as a whole.

Effect of test duration and feeding on relative sensitivity of genetically distinct clades of Hyalella azteca.

The amphipod Hyalella azteca is widely used in ecotoxicology laboratories for the assessment of chemical risks to aquatic environments, and it is a cryptic species complex with a number of genetically distinct strains found in wild populations. While it would be valuable to note differences in contaminant sensitivity among different strains collected from various field sites, those findings would be influenced by acclimation of the populations to local conditions. In addition, potential differences in metabolism or lipid storage among different strains may confound assessment of sensitivity in unfed acute toxicity tests. In the present study, our aim was to assess whether there are genetic differences in contaminant sensitivity among three cryptic provisional species of H. azteca. Therefore, we used organisms cultured under the same conditions, assessed their ability to survive for extended periods without food, and conducted fed and unfed acute toxicity tests with two anions (nitrate and chloride) whose toxicities are not expected to be altered by the addition of food. We found that the three genetically distinct clades of H. azteca had substantially different responses to starvation, and the presence/absence of food during acute toxicity tests had a strong role in determining the relative sensitivity of the three clades. In fed tests, where starvation was no longer a potential stressor, significant differences in sensitivity were still observed among the three clades. In light of these differences in sensitivity, we suggest that ecotoxicology laboratories consider using a provisional species in toxicity tests that is a regionally appropriate surrogate.