Evaluation of methyl bromide exposure on the plant quarantine fumigators by environmental and biological monitoring.

The study was undertaken to assess the potential risk of exposure to methyl bromide (MB) gas of plant quarantine fumigators who wore full facepiece gas masks with respirator canisters. The mean ambient concentrations of MB determined by a personal sampling device exceeded the TLV-ACGIH level of 5 ppm in the degassing processes at three fumigation sites except at the silos. The mean urinary bromine concentration of 379 non-MB workers was 6.3 +/- 2.5 mg/l with 95% confidence limits of 10 mg/l. There were 44.6% of 251 MB workers whose urinary bromine levels exceeded the 10 mg/l. There was a significantly positive correlation between the urinary bromine concentrations of the MB workers and the ambient MB concentrations in the degassing process. The MB levels in the workers' exhalation were positive in the degassing process, while those were below the detection limit in the dispersion process. Three possible routes through which the workers are exposed to MB gas are considered to exist: leakage through the interstice between the facepiece of a gas mask and the wearer's face, breakthrough of MB gas in the respirator canister, and percutaneous absorption of MB gas. Biological monitoring of urinary bromine and exhalatory MB as well as environmental monitoring of the ambient MB provided useful information for evaluating exposure of workers to MB.

[Determination of bromide ions in total blood, plasma and urine by ion chromatography with amperometric detection].

A direct injection method is described for the determination of bromide ions in plasma and urine by ion chromatography. After being diluted 10-20 times with eluent, the sample was directly injected into an ion chromatograph equipped with amperometric detection. Calibration curves were obtained in the range of 0.05 to 5 micrograms/ml of bromide ions. The coefficient of variation was calculated to be in the range of 1.3-9.4% for 10 repeated measurements and recovery was over 93%. The correlation between analytical results by the proposed method (Y) and those by a spectrophotometric method (X) of 169 urine samples in fumigators was expressed by the equation Y = 0.952 + 1.012X (correlation coefficient (r): 0.952). On the other hand, the correlation between analytical results by the proposed method (Y) and those by neutron activation analysis (X) of 47 total-blood samples in fumigators was expressed by the equation Y = 1.070 + 0.841 X (correlation coefficient (r): 0.931). The correlation between analytical results by the proposed method (Y) and those by neutron activation analysis (X) of 40 plasma samples in healthy workers was expressed by the equation Y = 0.633 + 0.871 X (correlation coefficient (r): 0.955). The proposed method is much more practical than other methods such as the spectrophotometric method and neutron activation analysis in epidemiological studies, because the proposed method is highly accurate and reproducible over longer periods. The proposed method is useful in biological fluid monitoring of bromide ions.

Efficiency of respirator canisters with methyl bromide.

Two kinds of respirator canisters, an organic vapor (OV) canister containing activated carbon and a methyl bromide (MB) canister containing activated carbon impregnated with triethylenediamine were investigated for their filtration efficiency of MB gas under various conditions of MB concentration, humidity and temperature. At lower MB concentrations, the breakthrough time of the OV canister was shorter than that of the MB canister. It also decreased with an increase in temperature, whereas the breakthrough time of the MB canister did not change with temperature. Humidity affected the breakthrough times of the OV canister as much as those of the MB canister. The desorption and the remaining filtration efficiency of MB gas were examined in both canisters which had been used for fumigation in plant quarantine. More than 5 ppm of MB gas leaked from 11 out of 18 used OV canisters, whereas less than 0.1 ppm MB leaked out from each of the used MB canisters. The mean remaining breakthrough time of the used OV canisters was 9.3 min, whereas that of the used MB canisters was 74.4 min. From the present study, it was shown that the gas masks with the OV canisters were not suitable for fumigating with MB gas.