Abstract
BACKGROUND
Hydrogen sulphide, a harmful gas produced in the wastewater treatment process, poses a daily risk to workers at wastewater treatment plants. It is colourless, and at higher concentration levels, its odour becomes undetectable. Exposure causes workers to experience headaches, difficulty breathing, eye irritation, and could even lead to death. With hydrogen sulphide, concentration levels are much more important than the duration of exposure. This study aimed to determine the hydrogen sulphide concentration levels in the working environment and its effects by describing the self-reported health outcomes. Additionally, it aimed to evaluate the relationship between the self-reported health effects and hydrogen sulphide among municipal sewage workers in the City of Johannesburg metropolitan municipality within the Gauteng Province.
METHODOLOGY
A descriptive cross-sectional analytical study was conducted on six wastewater treatment works within the City of Johannesburg. The study was conducted among randomly selected wastewater treatment workers between the ages of 21 and 65 years. These workers were employed in different units within the plants and had diverse educational backgrounds ranging from a primary level of education to employees with degrees. The participants resided in different geographical settings. Participants completed a structured self-administered questionnaire to determine any association between hydrogen sulphide exposure and self-reported health outcomes. Hydrogen sulphide concentration levels were measured in the ambient air within three different distances from operational sections for an eight-hour shift using a Wintact Compound Gas Monitor. The questionnaires and the environmental concentration results were entered into an Excel spreadsheet and imported into the latest IBM SPSS Statistics program for coding, data cleaning, and analysis. The researcher obtained scientific and ethical clearance from the University of Johannesburg. Permission to obtain data was granted from the City of Johannesburg.
RESULTS
Hydrogen sulphide concentration levels in the ambient air ranged from 0.99 ppm (parts per million) to 39.97 ppm, with a mean of 12.83 ppm and a standard deviation (SD) of 8.72 at a 5-meter distance, which is above the South African and international recommended exposure
iii
limit for an eight-hour shift. The self-reported health outcomes indicated that 35% of the participants suffer from tiredness, while 33 % suffer from eye irritation. The results also showed that 33% of the participants experienced headaches. The bivariate analysis showed that experiencing a burning sensation in the chest has a positive correlation with hydrogen sulphide levels within 10 meters and 15 meters.
CONCLUSION
This study is the first to report on the health effects of hydrogen sulphide exposure in the wastewater treatment works within the City of Johannesburg Metropolitan Municipality. The results provide evidence of a correlation between hydrogen sulphide exposure and self-reported health outcomes. The study also highlights that hydrogen sulphide concentration levels are much higher closer to the source. Even with the current international and local legislation, employees are still exposed to higher levels of the toxic gas.
KEY CONCEPTS
Hydrogen sulphide exposure, hydrogen sulphide concentration levels, wastewater treatment works workers, risk factors, and health outcomes.