Health Hazard Evaluation Report HETA 93-0012-2711, U.S. Department of Agriculture, Animal and Plant Health Inspection Service, Raleigh, North Carolina.
NIOSH, 1998 Oct :1-16
Officers of the U.S. Department of Agriculture's witchweed eradication program spot-fumigate small areas of land to kill witchweed seeds. A spot fumigation involves puncturing a pressurized 1.5-pound can of 98% methyl bromide and 2% chloropicrin under a plastic tarp covering an area of 10 feet by 15 feet. (Chloropicrin is added as a warning agent because methyl bromide has poor warning properties.) After waiting at least 48 hours, an officer removes the tarp. Because of a concern that methyl bromide exposures may still occur after the waiting period, the director of the witchweed eradication program requested a National Institute for Occupational Safety and Health (NIOSH) health hazard evaluation of the spot-fumigation process. During a pilot study, methyl bromide was measured under tarps at 27 hours and 47 hours after two spot fumigations were started on packed soil. Methyl bromide and chloropicrin measurements were later taken under six spot-fumigation tarps covering tilled soil. After five days, one tarp was removed, and two others were cut for auction. Methyl bromide and chloropicrin measurements were taken under three remaining intact tarps at two weeks after starting. Air sampling for methyl bromide was done according to NIOSH Method 2520 and using short -term detector tubes. Air sampling for chloropicrin was done using an Occupational Safety and Health Administration (OSHA) stopgap method. NIOSH considers methyl bromide a potential occupational carcinogen. OSHA's permissible exposure limit is a ceiling value of 20 parts per million (ppm). The Environmental Protection Agency (EPA) requires that workers wear respiratory protection any time methyl bromide exposures exceed 5 ppm. The American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Value (trademark) is a time-weighted average (TWA) of 1 ppm. For chloropicrin, NIOSH, OSHA, and ACGIH exposure limits are a TWA of 0.1 ppm, and EPA requires respirator use any time this concentration is exceeded.
Agricultural-workers; Herbicides; Exposure-levels; Hazard-Confirmed; Region-4;
Hazard Evaluation and Technical Assistance;
NTIS Accession No.
National Institute for Occupational Safety and Health