Comparison of 3 methods characterizing H2S exposure in water and wastewater management work.

This study evaluates the effectiveness of self-assessed exposure (SAE) data collection for characterization of hydrogen sulfide (H2S) risks in water and wastewater management, challenging the adequacy of traditional random or campaign sampling strategies. We compared 3 datasets derived from distinct strategies: expert data with activity metadata (A), SAE without metadata (B), and SAE with logbook metadata (C). The findings reveal that standard practices of random sampling (dataset A) fail to capture the sporadic nature of H2S exposure. Instead, SAE methods enhanced by logbook metadata and supported by reliable detection and calibration infrastructure (datasets B and C) are more effective. When assessing risk, particularly peak exposure risks, it is crucial to adopt measures that capture exposure variability, such as the range and standard deviations. This finer assessment is vital where high H2S peaks occur in confined spaces. Risk assessment should incorporate indices that account for peak exposure, utilizing variability measures like range and standard or geometric standard deviation to reflect the actual risk more accurately. For large datasets, a histogram is just as useful as statistical measures. This approach has revealed that not only wastewater workers but also water distribution network workers, can face unexpectedly high H2S levels when accessing confined underground spaces. Our research underscores the need for continuous monitoring with personal electrochemical gas detector alarm systems, particularly in environments with variable and potentially hazardous exposure levels.

Airway Symptoms among Farmers in Central Norway. A Comparative Study of Risks. The HUNT Study.

OBJECTIVES: The objective of this study was to compare the risk of developing respiratory symptoms in farmers and other occupational groups over a period of 11 to 23 years. METHODS: The study includes data from questionnaires and interviews in HUNT1-3 in The Trøndelag Health study (HUNT). In all three surveys, farmers can be identified. Two control groups are used. Control group 1 consists of all HUNT participants who are not farmers or fishermen. Control group 2 consists of occupational groups who presumably have low exposure to dust, chemicals or gases, but similar educational status as farmers. The data are analysed in SPSS 25 (IBM, Armonk NY), with use of frequency analyses and multiple binary logistic regressions. RESULTS: Our main finding is that healthy farmers have increased risk of developing respiratory symptoms as wheezing or breathlessness over a period of 11 and 23 years. This increased risk is statistically significant after 11 years of follow-up (HUNT1 to HUNT2), and also after 23 years (HUNT1 to HUNT3). Corresponding results regarding wheezing and breathlessness are found for healthy farmers in HUNT2 after 12 years of follow-up in HUNT3. In a subgroup analysis, we find a highly significant difference in both wheezing and shortness of breath when at work, in believing that the symptoms are caused by work, and in having to change jobs or quit because of breathing problems. CONCLUSION: Farmers have more respiratory symptoms than controls, and the main symptom is attacks of wheezing or breathlessness. Preventive measures such as ventilation and respiratory protection should be implemented on the farm.

Risk Characteristics of Hydrogen Sulphide Exposure in Wastewater Collection and Treatment Related Occupations.

OBJECTIVES: Water and wastewater workers can be exposed to hydrogen sulphide (H2S), with an unpredictable exposure pattern, dominated by sharp peaks. These peaks can often be high above the ceiling value (CV) at 10 ppm. METHODS: We have analyzed self-administrated H2S exposure data among 60 wastewater workers in the Municipality of Trondheim, Norway, from 2015 till 2021. The detection range of the personal alarm equipment used was 1.6 to 100 ppm H2S. The workers were divided in four similar exposed groups (SEGs): wastewater collection net, wastewater treatment plants, wastewater pumping stations and water distribution net. RESULTS: We identified measurements from 7083 different workdays, approximately 10% of the workdays between 2015 and 2021. Within these, 1295 days had readings above 1.6 ppm H2S, and 424 (33%) of these days had readings that exceeded the CV of 10 ppm H2S. This percentage was similar across the SEGs. Only one workday had a time weighted average (TWA) exceeding the occupational exposure limit (OEL) of 5 ppm H2S, and only 14 days exceeded 0.5 ppm H2S, 1/10th of the OEL. CONCLUSIONS: Wastewater workers in this study are regularly exposed to short peaks of H2S, but even high peaks do not influence the 8-h TWA values significantly. A preliminary measurement program over 3 days according to EN 689 to evaluate the need for further measurements would probably not find TWA values greater than 1/10 of OEL; the EN 689 standard is not made for evaluation to peak exposures. Exceedances of CV at 10 ppm H2S occur in 6% of workdays, and in 33% of days with exposure above 1.6 ppm. The toxicity and exposure profile of H2S makes continuous exposure monitoring necessary for alarm purposes. Reliance on the 8-h occupational exposure limit as has been the normal in Norway, will not be adequately protective for wastewater workers. H2S alarm equipment should continue to be used.