The effect of mineral oil exposure on metal workers at a large engineering plant in Bloemfontein, South Africa

Abstract

Adverse and chronic pulmonary health effects have been associated with workers exposed to various types of metal working fluids (MWF's). Within South Africa there is a lack of research dealing with specific agents in MWF's which may be the source of pulmonary health problems. This occupational health study deals with the acute pulmonary health effects ofMWF's among metal workers employed by an engineering company in South Africa. A cross-sectional population of341 machine workers was sampled for full shift personal exposures to MWF's according to a modified National Institute for Occupational Safety and Health Method (NI0SH) Number 0500. Forced expiratory volume in one second (FEV,) tests were completed before and after the worker's shift according to manoeuvers dictated by the American Thoracic Society (A TS). A written health survey comprised from the British Medical Research Council and the International Union Against Tuberculosis and Lung Diseases questionnaire, was utilised to determine the worker's present health condition during the study. Personal inhalation exposures were lower than the current 1999 American Conference of Governmental Industrial Hygienists Threshold Limit Value (ACGIH TLV) of 5 mg/m3 (mean = 1.04 mg/m3 , arithmetic standard deviation = 2.0). However, increasing personal exposures to MWF's were positively correlated to decreases in FEV, (plant 1: r = 0.96, Plant 2: r = 0.94, Plant 3: r = 0.97). The change in FEV, of nonsmoking workers exposed to MWF's was significantly different in comparison to unexposed nonsmoking workers (ANOVA, P = 0.05, n = 297). Similarly, nonsmoking workers who were exposed to MWF's with higher fractions of triethanolamine (TEA) and diethanolamine (DEA) had greater decreases in FEV, (ANOV A, P = 0.02, n = 183). Workers who were current smokers and exposed to MWF's experienced the highest decreases in FEV, in comparison to exposed nonsmoking workers (ANOV A, P = 0.05, n = 341). Workers exposed to the four types of MWF' s experienced a logarithmic dose-response to the decrease in FEV,. This dose-response was explained with a mathematical equation for each MWF type. Permissible safe limits derived from these equations (MWF Type l: 1.70 mglm' , MWF Type 2: 0.41 mglm', MWF Type 3: 0.29 mglm' and MWF Type 4: 0.D35 mglm') reflect the validity ofNIOSH's recommendation of a safe exposure limit of 0.5 mglm'- It is concluded that workers who are exposed to MWF's, experience acute decreases in FEY,. Similarly, workers who are smokers and exposed to TEA- and DEA MWF's experience the greatest decrease in FEY,. Engineering controls, and use of highly refined MWF's containing no DEA and TEA were recommended to the engineering company.