Diquat is a herbicide that has been used extensively in the United States since

Question

Diquat is a herbicide that has been used extensively in the United States since the late 1950s. Consult the IRIS database (EPA Integrated Risk Information System. http://www.epa.gov/iris/). What is the No Observed Adverse Effect Level (NOAEL) for diaquat? What is the critical effect (health hazard)? What uncertainty factors were applied to the NOAEL level to determine the RfD? Determine the DWEL for diquat based on the reference dose (Rfd). Determine an MCLG assuming a relative source contribution of 20% - i.e., 20% of human exposure is from drinking water. Compare your calculation to the EPA MCL for diquat.

Explanation / Answer

Part-a: NOAEL is defined as the highest non-clinical experimental point where a dose of an agent causes no adverse effect upon usage. In the above case, NOAEFL for diaquat herbicide for rat specifmens are 0.58 mg diquat ion/kg bw per day for rats where as lowest oral NOAEFL for diaquat is 0.53 mg diquat ion/kg body weight per day as pr EPA integrate risk information system

Part-b: Critical effect is defined as the toxicological effect where it causes adverse effect to the health of an organism and critical effect produced by this diaquat in rats due to exposure higher than 0.53mg resulted in "cataract" and carcinogenecity. In case of humans, risk of developing cancer when exposed to this herbicide

Part-c: Reference dose (RfD) of diaquat is determined based on the toxicity levels induced to the plant as a herbicide. RfD also can be determined based on the toxicity levels produced when "no observed adverse effect level (NOAEL)" for diaquat with uncertainity factors such as "interspecies uncertainty factor" or the "intraspecies uncertainty factor" due to adverse effects caused to humans

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