The effect of aerosol exposure on foundry workers and arc welders at a large engineering plant in South Africa

Abstract

South African data regarding the extent of aerosol exposure and health effects in the workplace are limited . Furthermore, a shortage of industrial hygiene- and epidemiological data from large scale studies exist. Given the increasing concern about the health of industrial metal workers, an inhalation exposure study of South African iron foundry workers and welders at a large engineering plant in Bloemfontein, was undertaken. The aim of the study was to compile a source inventory, identifying and characterising all health related inorganic aerosols to which metal workers of the plant are potentially or actually exposed. In addition, the exposure risk was assessed by the integration of aerosol concentrations and biological data from urine analyses. Aerosols were sampled by means of time sequence particulate sampling on streaker filter frames and analysed with Particle Induced X-ray Emission (PIXE) on the Tandem van de Graaff accelerator of the University of the Witwatersrand, Johannesburg. The streaker is analysed in 1 mm steps, corresponding to 1 hour of exposure. PIXE analysis yielded concentrations or detection limits of elements AI, Si , P, S, CI , K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, In, Br and Pb. The urine of selected exposed workers was sampled according to NIOSH method 8310 and analysed using Atomic Absorption (AA) spectrometry for the urine-metal concentrations In, Cd, Co, Ni, Mn, Cu, Cr, AI , Fe, Pb, Si and V. Forced vital capacity (FVC), forced expiratory volume in one second (FEV1 ), peak expiratory flow (PEF), peak inspiratory flow (PIF), average expiratory flow between 25 % and 75 % of FVC (FEF2s-7S), expiratory flow at 25 % of FVC (Vma>e2S), expiratory flow at 50 % of FVC (VmaxSO) , expiratory flow at 75 % of FVC (Vmax7s) and forced expiration time (100 % FVC) (FET1oo), was conducted with a Cosmed Pony spirometer. This was done to provide a physical image of the workers' lungs. A new method for the assessment of aerosol inhalation exposure risk, called AIER, using aerosol concentrations and metal urine concentrations, is proposed for estimation of the inhalation risk. The assumptions and calculation for the new method are presented. A number of sources or source categories have been identified in the foundry's and welding shop's air by making use of patterns of time variations and elemental ratios. Six sources namely crustal particles, sulphur, In-Pb-CI, two distinct components of different castings and other heavy metals were identified as sources. The main pollutants and the relative contributions from other sources have been identified for iron foundries and welding shops with recognised air quality problems. Overexposure occurred during specific operations which was also quantified for rectification. The urine analysis of the foundry workers yielded high concentrations of Cd, Cu, Fe and Si. It is assumed that the Fe and Si concentrations are exposure related. The analysis of urine from the welders yielded high concentrations of Ni, Cr and Fe. Although Ni concentrations in the workroom air were low, the occurrence of all three elements in the urine may ·be as a result of chronic exposure to welding fumes in their workplace. Except for vanadium, no statistical significant differences (P > 0.05) were found between the different metal urine concentrations of the workers of the two localities. The total exposed foundry population showed a significant decrease in FEV1 and FVC which indicates that the pollution in the workplace contributes to the development of restrictive lung disorders in foundry workers. The dust created during the welding of steel in the welding shop is a contributing agent in the development of obstructive respiratory disorders in the welder population. Examination of the relationship between elemental variations has allowed identification of several sources and activities contributing to airborne particles. The aerosol profiles did not show similar diurnal time variation patterns in the foundry or the welding shop due to irregularities in the continuation of the processes. The AIER for the foundry resulted in a maximum value of 92.3 % while the corresponding value for the welding environment was 71.7 %. The results present the worst case scenario during winter conditions and it is expected that conditions will be more healthy during summer time when windows and doors are open. The planning and prioritisation for the improvement of indoor air quality in both workplaces can proceed , using the data on the sources of the pollutants. It can be concluded that workers exposed to conditions as found during this project, will experience health problems after chronic exposure. The results emphasised the importance of exposure characterisation in order to provide for identification of pollutants, control of sources and the application of industrial hygiene principles for the protection of human health. It is recommended that all industries implement exposure characterisation programmes as a tool in applying good occupational and environmental hygiene.