Respiratory Exposure of Grain Inspection Workers to Carbon Tetrachloride Fumigant

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Carbon tetrachloride (often mixed with carbon disulfide or ethylene dichloride) is a common constituent of liquid grain fumigants. Applied as liquids, these mixtures volatilize and achieve vapor concentrations sufficient to control insect infestations in stored grains. Absorbed grain desorbs fumigant components after the fumigation period, and it then becomes a source of exposure to workers who handle fumigated grain. Carbon tetrachloride meets the EPA's risk criteria for hepatotoxicity, nephrotoxicity and oncogenicity, and it has been under regulatory review since 15 October 1980. Present OSHA standards for CCl4 are a time-weighted average (TWA) of 10 ppm and an acceptable ceiling of 25 ppm. ACGIH and NIOSH have recommended lowering the OSHA standard. The point at which peak exposure occurs during the grain inspection process has been identified as the off odor test in which the inspector smells the grain sample for rancidity, sourness, etc. Ambient concentrations of CCl4 in 7750 grain samples submitted for inspection were determined by colorimetric tube, and these concentrations were an estimate of peak grain inspector exposure to CCl4. The average ambient concentration of CCl4 per grain sample was 1.69 ppm±8.35. Approximately 380 TWA CCl4 exposures for grain inspection workers were determined by using passive dosimeters. All TWA exposures were less than 2 ppm. Variables are examined, such as location of work, grain type, time of year and grain transportation vehicle — all of which are known to the sampler or inspector before performing their job functions and which affect potential exposure.