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.

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.

Acute respiratory distress after exposure to chlorine dioxide-based disinfectant.

A hospital cleaner developed acute respiratory distress after working with a chlorine dioxide-based disinfectant. The content of chlorine dioxide in the product is below the limit that would require the product to be labelled as hazardous to health, but we show with a simple estimation that the relevant threshold limit values for chlorine dioxide in the working atmosphere may be exceeded under normal use of the product. This may have implications for risk assessment of the use of such chlorine dioxide-based disinfectants and may warrant stricter regulations for labelling these products.

Hydrogen Sulphide (H2S) Exposure Hazard Assessment: An Algorithm for Generating Exposure Index Based on Direct Instrument Readings.

OBJECTIVES: Increased use of small affordable alarm sensors with logging or network capabilities has improved the ability to monitor exposure. The large datasets generated from these monitors calls for development of a computer algorithm to assess these data. METHODS: We examined 88 time series of hydrogen sulphide (H2S) from wastewater works previously used for developing the exposure index. The time series covered 331 h, where 16 h had readings different from zero. RESULTS: The developed algorithm reproduced the manual assessed index almost perfectly (linear regression ß = 1.02, R2 = 0.97, P < 0.001). Time-weighted average (TWA) values of the 88 time series showed a mean value of 0.04 ppm (range 0.0-0.9). The mean index value was 18 (range 0-337), with a good linear fit (ß = 0.002, R2 = 0.93, and P < 0.001). The index gave us a better resolution and basis for risk assessment than the TWA, and managed to combine evaluation of TWA and exceedance of ceiling value in one number. CONCLUSIONS: As long as peaks above ceiling value occur, we find alarm tools with an H2S sensor to be an essential personal protective equipment against H2S. The proposed method has been verified, and it removes some common human errors in graph evaluation. Use of the index is a possible way of quantifying risk level in exposure to H2S in one single number and provides better understanding of the risk of exposure, as it eases the analysis and evaluation of large numbers of time series.

Allergic contact dermatitis caused by epoxy resin systems in industrial painters.

A group of industrial painters employed in 6 companies of the Norwegian oil industry was followed to assess the incidence of allergic contact dermatitis (ACD) caused by exposure to epoxy resin systems. The study lasted from 1 September 1997 to 31 August 2001 and included 2236 workers, contributing 5113 person years. Commercially available patch test series were supplemented with a special study series based on known or suspected sensitizers present at the workplaces. Of 57 patch-tested workers, 23 with ACD caused by epoxy resin systems were found, indicating an incidence rate of 4.5/1000 person years. In our study patch test series, 4 workers (17%) were identified solely by patch tests to 2,4,6-tris-(dimethylaminomethyl)phenol (tris-DMP), m-xylene-alpha,alpha-diamine (XAD), and/or 2,2,4 trimethylhexamethylenediamine. Positive patch tests to tris-DMP and XAD were seen in 7 and 8 workers, respectively, indicating that the 2 chemicals are important sensitizers in industrial painters. They are, however, not classified as skin sensitizers according to the European regulations on the classification and labelling of dangerous chemicals. The results show the usefulness of including patch tests based on an investigation of known and suspected skin sensitizers present at the workplaces.

Relationships between indoor environments and nasal inflammation in nursing personnel.

In this study, the authors sought to address the relationships between measured indoor environmental factors and nasal patency (i.e., minimum cross-sectional area) and volume and markers of nasal inflammation in nasal lavage fluid. Clinical data were obtained for 115 females who worked at 36 geriatric nursing departments. The indoor climates in the nursing departments were characterized by high room temperatures (median = 23 degrees C), low relative air humidities (median = 24%), and high air exchange rates indicated by low carbon dioxide levels (median = 570 ppm). Evidence of microbial amplification was observed in the ventilation unit in 3 of the departments. Decreased nasal patency was observed relative to microbial amplification in the ventilation units (minimum cross-sectional area 1 = 0.80 cm2 vs. 0.64 cm2, p = .003, minimum cross-sectional area 2 = 0.80 cm2 vs. 0.67 cm2, p = .02) and in relation to elevated indoor temperature (volume 1 = 3.46 cm3 vs. 3.22 cm3, p = .03). The authors concluded that the indoor environment may have affected the nasal mucosa of nursing personnel, thus causing nasal mucosal swelling. The results support the view that fungal contamination of air-supply ducts may be a source of microbial pollution, which can affect the nasal mucosa.