Question

1.Consumers spraying their lawns for control of white grubs with the formulation Dursban prior to its removal from hardware stores like Home Depot and Ace were estimated to have a high end exposure of about 0.015 mg/kg/day. Considering that this product would only be applied once or twice a growing season, the margin of exposure (MOE) relative to the acute no observable adverse effect level (NOEL or NOAEL) of 0.5 mg/kg/day is [______]. This exposure is [_______] (above or lower) EPAs levels of concern (LOC).

2. Although Roundup is more toxic than its active ingredient alone, cause for concern should a wetland be oversprayed is unlikely due to a short persistence time of the toxicant causing this differential effect. The reason for this short persistence time is the presence in natural waters of [__________________].

3. The work of Tyrone Hayes at the University of California-Berkeley has suggested that atrazine herbicide disrupts the endocrine system. Some scientists suggest therefore that frogs should be used as “canaries in a coal mine” and forewarn us about the imminent danger that this herbicide poses to human fertility and development. The plausibility of such an extrapolation is weak for which of the following reasons. (Choose all reasons that support the lack of plausibility)

a.The aggregate of all research on atrazine in a quantitative weight of evidence meta analysis concluded that effects on amphibian development and growth were unlikely

b. Studies published subsequent to Hayes early research were not able to repeat the observations of effects on frogs

c. Atrazine residues are hardly ever found in food, thus exposures would be minimized.

d. Atrazine residues are hardly ever found in water, thus exposures would be minimized.

Answer 1

1. Consumers spraying their lawns for control of white grubs with the formulation Dursban prior to its removal from hardware stores like Home Depot and Ace were estimated to have a high end exposure of about 0.015 mg/kg/day. Considering that this product would only be applied once or twice a growing season, the margin of exposure (MOE) relative to the acute no observable adverse effect level (NOEL or NOAEL) of 0.5 mg/kg/day is [_33.33_]. This exposure is [_above _] EPAs levels of concern (LOC).

(MOE = NOAEL/Estimated Exposure Dose = 0.5/0.015 = 33.33

EPA's LOC for Dursban, is unacceptable at any level below 1000.)

2. Although Roundup is more toxic than its active ingredient alone, cause for concern should a wetland be oversprayed is unlikely due to a short persistence time of the toxicant causing this differential effect. The reason for this short persistence time is the presence in natural waters of [_microorganisms_].

(Roundup is brand name of Glyphosate. Its concentrations in natural water diminish rapidly due to microbial degradation, binding it to suspended particulate or dispersion.)

3. The work of Tyrone Hayes at the University of California-Berkeley has suggested that atrazine herbicide disrupts the endocrine system. Some scientists suggest therefore that frogs should be used as “canaries in a coal mine” and forewarn us about the imminent danger that this herbicide poses to human fertility and development. The plausibility of such an extrapolation is weak for which of the following reasons.

Options that suggests lack of plausibility:

a.The aggregate of all research on atrazine in a quantitative weight of evidence meta analysis concluded that effects on amphibian development and growth were unlikely.

b. Studies published subsequent to Hayes early research were not able to repeat the observations of effects on frogs.

(A 2003 EPA review of this study concluded that questionable techniques, made it difficult to assess the credibility of the study its ecological relevance. A 2008 report cited the independent work of researchers in Japan, who were unable to replicate Hayes' work. The EPA's Scientific Advisory Panel examined relevant studies and concluded in 2010, "atrazine does not adversely affect amphibian gonadal development ".)

Other options dont suggest lack of plausibility. Atrazine residues are found in food and water and its exposure consistently exceeds EPA levels of concern in some places.

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