Go to the EPA IRIS data base at http://www.epa.gov/iris . Right under the Integr

Question

Go to the EPA IRIS data base at http://www.epa.gov/iris . Right under the Integrated Risk Information System banner (or on the right, depending on which browser you are using), there is a search IRIS by keyword option. Please enter Bromomethane.   After reading the information on Bromomethane. Answer fully the following questions in your own words:

a.     What is meant by inhalation reference concentration?

b.     What types of studies did the EPA use to estimate the inhalation reference concentration? (human, animal, or both?)

c.     What was the adverse effect upon which the Agency based its estimate?

d.     What are the major uncertainties in the estimate?

e.     What additional studies would be needed to determine whether bromomethane should be classified as a carcinogen?

Explanation / Answer

(a) The inhalation reference concentration (RfC) for bromomethane is 5 x 103 mg/kg-day. RfC is the threshold level beyond which the inhalation of bromoethane will be toxic and cause respiratory and nervous problems. This reference value is based on the maximum limit to which the human population may be exposed to bromomethane without causing any harm, such as cellular necrosis.

(b) The EPA used animal studies using female and male rats to estimate the inhalation reference concentration.

(c) The adverse effects of bromomethane caused in the animal samples were epithelial lesions in nose cavity, cardiac lesions, histopathological outcome and in higher concentrations, organ toxicity and death. The Agency based its RfC estimate based on these adverse effects.

(d) The major uncertainty in the RfC estimate of bromomethane was whether the same effect was valid in different species and most importantly in humans. Also, the lifetime duration exposure of bromomethane would cause what type of complications could not be inferred.

(e) Animal of different species and human carcinogenicity tests should be performed extensively so as to determine whether bromomethane should be classified as a carcinogen or not.

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