Exposure of poultry farm workers to ammonia, particulate matter and microorganisms in the Potchefstroom district, South Africa
De Jager, Anna Catharina
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Motivation: The investigation of agricultural respiratory hazards has lagged behind the investigation of hazards in mining and other heavy industries. Relatively few epidemiological data are available addressing pulmonary infections in the context of the agricultural work environment, especially for the South African population. Poultry house dust was generally considered nuisance or inert, meaning it has little adverse effect on human lungs. New research shows that because poultry house dust is largely organic and contain bacteria and other bioactive substances, it cannot be considered inert. Several published research manuscripts document that the legal and recommended exposure limits for the toxic substances found in the agricultural environment are to high for concentrated animal feeding operations (CAFO's). In CAFO's there is a mixture of biologically active agents that can work synergistic to produce respiratory and systemic effects at much lower levels. Most of the current legal exposure limits used in South Africa are adopted from international limits and guidelines. Because of the influence of geography, climate and degree of industrialisation on the agricultural air quality, the relevance of the foreign exposure limits is questionable. Aim: To determine if there is a correlation between occupational exposure to poultry farm dust and the lung function of poultry farm workers in the Potchefstroom district, South Africa. Also to determine if the current legal exposure limits used for ammonia and particulate matter (PM) in South Africa, offer adequate worker protection for poultry farm workers exposed to biologically active dust. Methodology: This was an observational, cross-sectional pilot study. A target population of fifty contract workers concerned with the removal and disposal of poultry manure were identified in the Potchefstroom district and a random sample of nineteen was drawn for participation in this study. Exposure to total and respirable dust were determined by means of personal sampling for the full duration of the time averaging period (8-hour TWA). Area monitoring for ammonia and bio-aerosols were done in poultry houses in three specific demarcated areas around Potchefstroom, and weather conditions were taken into account. Lung function tests (spirometry) were conducted before and after each work shift. Interviewer administered questionnaires were used to assess occupational and exposure histories and to detect symptoms of organic dust exposure. Results and conclusions: The mean total- and respirable dust concentrations complied with the legal limits of OSHA, NlOSH and the Regulations for hazardous chemical substances of 1995. However, fifty five percent of the measured total dust concentrations and all of the respirable dust measurements exceeded Donham's recommended values for human health. The spirometric values of the subjects were normal; there was no statistical difference between the mean baseline FEV1/FVC and the mean predicted FEV1/FVC. Results also show no statistically significant cross shift changes in any of the measured variables and there is no significant correlation of the measured dust concentrations to any of the spirometric measurements. It can be concluded that occupational exposure to ammonia, particulate matter and micro-organisms on poultry farms in the Potchefsroom district, South Africa, do not have any adverse effects on the workers' lung function and the workers are adequately protected in the short term, by the legal limits that are currently used in South Africa.
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