携帯オイルミスト用サンプラーによる気中濃度測定と作業者の自覚症状:機械工場における調査研究

抄録

Machine oils are widely used in metal processing and many workers are exposed to oil mists in the work environment. Some investigators have pointed out such health hazards due to prolonged exposure to oil mist as respiratory disorders, dermatitis, and possible carcinogenesis. In Japan, a permissible limit of oil mists of 3 mg/m³ was recommended in 1977 by the Japan Association of Industrial Health (JAIH) mainly based on the hazardous effects on the respiratory system. After this recommendation was made, only a few studies have been made on the measurement of oil mists and on the health effects in machine workers to deterimine whether the the permissible limit is justifiable or not. In the present study, the levels of oil mists in the air of machine workshops were measured together with personal exposure levels by personal samplers. Oil mists were collected by a sampler head with 2 stages which enabled differentiation of distribution of particulates between larger than 10 μm and 2-10 μm in size. Oil components collected on the stainless steel stages were washed out by sonication in CCl₄ solution and measured by an oil meter with infra-red spectrometry against a standard solution of heavy oil class B according to procedures reported elsewhere by the authors. Questionnaire surveys were also conducted on 308 male machine workers composed of 221 workers exposed to oil mists and 87 nonexposed controls. The questions were composed of five items about air quality in the work environment and 18 subjective symptoms during work and daily lives. The symptoms included nasopharyngeal, muco-dermal, gastrointestinal and neuro-muscular symptoms. Statistical analysis was made by the Manthel-Haenszel method for a comparison of “yes” rates of complaints between the exposed and the non-exposed by adjusting the underlying confounding factor of age distribution.
1. The levels of oil mists measured here ranged from 94 to 813 μg/m³ in the ambient air and from 107 to 483 μg/m³ of personal exposure. There was no obvious difference between the level in the ambient air and that of personal exposure. All these measured levels were under the permissible limit (3 mg/m³) recommended by JAIH in 1977.
2. The observed distribution of particulate size of oil mists from 2 to 10 μm referred to as respirable size was 32.8±16.1% generated from the grinding machines using water-soluble type of machine oils and 50.0±12.4% from those using insoluble type.
3. The exposed group complained of “a hazy air, ” “wish to use fans” and “disagreeable smell” in the work environment at a higher rate than the non-exposed with a statistical difference (p<0.05). The above 3 items showed greater “yes” responses among the higher exposed group (495-813 μg/m³) than the group exposed to lower level (94-430 μg/m³) and the non-exposed group in descending order.
4. The higher the exposure level, the more “yes” responses were observed in the questions regarding “nose irritation” and “unpleasant taste” during work and daily lives.
The results obtained suggest that workers dealing with machine oils complained of dissatisfaction with their work environment even below the permissible limit for oil mists. The combined assessment made by the measurement of the levels of oil mists and the questionnaire survey of subjective symptoms among workers is considered to be a useful strategy for the prevention of health hazards and the improvement in the amenity of work environment.