the recommended threshhold limit value ( TLV-ACGIH) air concentration for occupa
ID: 1919959 • Letter: T
Question
the recommended threshhold limit value ( TLV-ACGIH) air concentration for occupational exposure to water-insoluble hexavalent chromium Cr (VI) is 0.01 mg/M^3. this concentration is based on an assumption that the individual is generally healthy and is exposed for 8 hours per day over a working lifetime ( that is from age 18 to 65 years). assuming a body weight of 78 kg and an inhalation rate of 0.63 m^3/h over the working life of the individual,
a. what is the lifetime (75y) CDI?
b. estimate the low-dose cancer risk from occupational inhalation exposure to hexavalent chromium.
Explanation / Answer
(a)
The drinking water of the town of Watsford, NY contains the USEPA maximum levels of benzene, benzo(a)pyrene, and arsenic. While these levels are safe by USEPA standards, a risk assessment was performed to determine if there is an increased risk of developing cancer for a resident of Watsford.The Chronic Daily Intake (CDI) of each pollutant and total risk were calculated for a female resident with a life expectancy of 75 years and an average weight of 65.4kg. Six exposure pathways were used involving exposure during drinking, swimming, and showering. The total risk was calculated to be x.xx,and the CDI and risk associated with yyyyy was the highest of the three contaminates. The calculations required several assumptions involving the physical details and daily actions of the subject. During the calculations, it was required to account for all realistic pathways and variables;the calculations cannot fit each person individually.
(b)
Chromium occurs in the environment primarily in two valence states, trivalent chromium (Cr III) and hexavalent chromium (Cr VI). Exposure may occur from natural or industrial sources of chromium. Chromium III is much less toxic than chromium (VI). The respiratory tract is also the major target organ for chromium (III) toxicity, similar to chromium (VI). Chromium (III) is an essential element in humans. The body can detoxify some amount of chromium (VI) to chromium (III).
The respiratory tract is the major target organ for chromium (VI) toxicity, for acute (short-term) and chronic (long-term) inhalation exposures. Shortness of breath, coughing, and wheezing were reported from a case of acute exposure to chromium (VI), while perforations and ulcerations of the septum, bronchitis, decreased pulmonary function, pneumonia, and other respiratory effects have been noted from chronic exposure. Human studies have clearly established that inhaled chromium (VI) is a human carcinogen, resulting in an increased risk of lung cancer. Animal studies have shown chromium (VI) to cause lung tumors via inhalation exposure.
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