Monitoring of air for microbial and metal contamination at selected sites in the vicinity of Johannesburg, South Africa.

A preliminary survey was undertaken to identify air contamination in the vicinity of industrial, residential and hospital sites. In many developing countries, poor town planning has resulted in growth of residential and commercial sites in close proximity to the industrial works, without the provision of a buffer zone. As prevailing winds blow across the industrial works to the other areas, undesirable pollution may be experienced. Before steps are taken to reduce factory emissions, the impact of the industry on the surrounding area needs to be clearly defined. In this study, the total particulate matter and the level of microbial contamination at the selected sites is reported. The elemental composition of the particulate matter is described.

Fluoride in workplace air and in urine of workers concentrating fluorspar.

The urinary fluoride concentrations of workers exposed to calcium fluoride (CaF2) during fluorspar processing were measured. Personal dust measurement showed that the mean occupational exposure to fluoride for 12 workers in the most dusty environment was 24.3 mg/m3, which is 9.7 times the threshold limit value (TLV) of 2.5 mg/m3. Exposure was below the TLV for the remaining 23 workers. Urinary fluoride concentrations were measured pre- and postshift. The heavily exposed workers had a mean preshift concentration of 3.3 mg/liter (range 1.4-8.5 mg/liter), only slightly higher than the mean of 2.8 mg/liter (range 1.3-4.2 mg/liter) in the workers with fluoride exposure below the TLV. Four of the preshift concentrations exceeded the recommended upper limit of 4 mg/liter. The mean postshift concentration for workers exposed above the TLV was 4.4 mg/liter (range 2.4-7.1 mg/liter) and the difference between pre- and postshift concentrations was significant (p less than 0.05). Only one urinary concentration exceeded the recommended upper limit of 7 mg/liter. There was poor correlation between intensity of environmental exposure to fluorspar and postshift fluoride concentration in the urine. Eighteen workers provided a urine sample 7-14 hr after the end of a shift. The mean fluoride concentration was 4.7 mg/liter (range 2.4-11.7 mg/liter), which exceeded their postshift concentration by 0.2 mg/liter. These results indicate that the low aqueous solubility of fluorspar reduced the biologic availability of the fluoride ion but that this did not prevent excessive fluoride absorption in some workers.