Association of lymphocyte count and serum albumin concentration with telomere length in Chinese sanitation workers

OBJECTIVE

This study aimed to examine the association between inflammation-related indicators (IRIs) and telomere length (TL) in Chinese sanitation workers.

METHODS

This study adopted a case-control design, conducted from January to December 2022 in Shenzhen, a city in eastern China. A total of 80 sanitation workers, as well as 80 matched controls, were randomly recruited from the Luohu district of Shenzhen city in China. Their blood samples were collected and analyzed for the IRIs and TL in the Medical Laboratory of Shenzhen Prevention and Treatment Center for Occupational Diseases. The relationship between IRIs and TL was analyzed using multivariate linear regression, and their dose-response relationship was explored using restricted cubic spline analysis.

RESULTS

The systemic inflammatory index (SII), platelet-to-lymphocyte ratio (PLR), and neutrophil-to-lymphocyte ratio (NLR) were significantly elevated in the sanitation workers in comparison to the controls. Moreover, the lymphocyte count (LYM), serum albumin concentration (ALB), and TL were found to be lower in the sanitation workers compared to the controls (P < 0.05). After adjusting for potential confounding variables, LYM was negatively correlated with TL in the sanitation workers (β = -0.31, 95% CI: -0.57, -0.05), whereas no correlation was observed in the controls. Furthermore, ALB demonstrated a non-linear relationship with TL in sanitation workers.

CONCLUSION

We found higher novel inflammatory markers (SII, PLR, and NLR) in the sanitation workers, and identified a correlation between LYM and ALB with shortened TL in them, providing new evidence for the effect of elevated inflammation on accelerated aging in Chinese sanitation workers.

Microbiological aspects of sewage odor problems in the urban environment - a review

Growing human population and increasing urbanization call for the need for proper wastewater treatment to reduce environmental pollution and reduce the excess use of natural resources. During the collection of municipal wastewater, the rapid aerobic respiration often causes oxygen depletion and anaerobic conditions in the sewer system resulting in the production of malodorous compounds. The odor problems may lead to public complaints, or in the case of the sewage workers the released volatile compounds even cause serious health hazards. Therefore, microbes have a dual contribution in the urban water cycle, since they have a decisive role in wastewater treatment and the removal of pollutants, but they can also cause problems in the artificial environment. In this review, I would like to summarize the processes underlying the generation of the bad smell associated with sewage and wastewater or with the collection and treatment infrastructure, tracking the way from the households to the plants, including the discussion of processes and possible mitigation related to the released hydrogen sulfide, volatile organics and other compounds.

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.

Global systematic review of occupational health and safety outcomes among sanitation and hygiene workers

Introduction

Sanitary workers are exposed to a variety of occupational hazards in a variety of working environments, which can result in occupational-related outcomes. As a result, the goal of this review was to identify occupational health and safety outcomes among sanitary workers worldwide.

Methods

PRISMA was used as flow diagram and PICOS was used review questions. The studies published in English were searched from databases and others methods ranging from 2000 to 2022. Boolean logic (AND, OR), MeSH, and keywords used: (Occupation *OR Job *OR Work) AND (Occupational related respiratory Symptoms *OR Disease) AND [Solid waste collectors (SWCs) *OR Street sweepers (SS) *OR Sewage workers and waste treatment (STWs)] AND (Countries).

Results

A total of 228 studies were identified from 23 countries across the world. Studies were found via PubMed (n = 40), Medline (n = 25), Embase (n = 11) and Global Health (n = 66) and Google scholar (n = 63) and from previous (n = 23). From 8,962 of eligible sanitary workers, about 4,742 (54%), 1714 (19%) and 1,441 (16%) were sewage, sweepers and solid waste workers, respectively. A total study (n = 51) were eligible for occupational health and safety outcomes. Of these, respiratory problems accounted 27 (52%) and Gastroenteritis 14 (27%).

Conclusion

Despite a large number of studies to date provides sanitary employees all over the world face occupational-related risks, hence more research is needed to enhance and quantify illness burden among sanitary workers.

Health symptoms, inflammation, and bioaerosol exposure in workers at biowaste pretreatment plants

Biowaste pretreatment plants have been built within the last years in Denmark in order to recycle pre-sorted biowaste from houses, restaurants, and industry. We investigated the association between exposure and health at six biowaste pretreatment plants (visited twice) across Denmark. We measured the personal bioaerosol exposure, took blood samples, and administered a questionnaire. Thirty-one persons participated, 17 of them twice, resulting in 45 bioaerosol samples, 40 blood samples, and questionnaire answers from 21 persons. We measured exposure to bacteria, fungi, dust, and endotoxin, the total inflammatory potential of the exposures, and serum levels of the inflammatory markers serum amyloid A (SAA), high sensitivity C-reactive protein (hsCRP), and human club cell protein (CC16). Higher exposures to fungi and endotoxin were found for workers with tasks inside the production area compared to workers with main tasks in the office area. A positive association was found between the concentration of anaerobic bacteria and hsCRP and SAA, whereas bacteria and endotoxin were inversely associated with hsCRP and SAA. A positive association between hsCRP and the fungal species Penicillium digitatum and P. camemberti were found, whereas an inverse association between hsCRP and Aspergillus niger and P. italicum were found. Staff with tasks inside the production area reported more symptoms of the nose than those working in the office area. To conclude, our results indicate that workers with tasks inside the production area are exposed to elevated levels of bioaerosols, and that this may affect workers' health negatively.

Low level exposure to hydrogen sulfide: a review of emissions, community exposure, health effects, and exposure guidelines

Hydrogen sulfide (H2S) is a toxic gas that is well-known for its acute health risks in occupational settings, but less is known about effects of chronic and low-level exposures. This critical review investigates toxicological and experimental studies, exposure sources, standards, and epidemiological studies pertaining to chronic exposure to H2S from both natural and anthropogenic sources. H2S releases, while poorly documented, appear to have increased in recent years from oil and gas and possibly other facilities. Chronic exposures below 10 ppm have long been associated with odor aversion, ocular, nasal, respiratory and neurological effects. However, exposure to much lower levels, below 0.03 ppm (30 ppb), has been associated with increased prevalence of neurological effects, and increments below 0.001 ppm (1 ppb) in H2S concentrations have been associated with ocular, nasal, and respiratory effects. Many of the studies in the epidemiological literature are limited by exposure measurement error, co-pollutant exposures and potential confounding, small sample size, and concerns of representativeness, and studies have yet to consider vulnerable populations. Long-term community-based studies are needed to confirm the low concentration findings and to refine exposure guidelines. Revised guidelines that incorporate both short- and long-term limits are needed to protect communities, especially sensitive populations living near H2S sources.

A cohort study of wastewater treatment plant workers: Association between levels of biomarkers of systemic inflammation and exposure to bacteria and fungi, and endotoxin as measured using two methods

Work in wastewater treatment plants (WWTPs) can be associated with exposure to airborne microorganisms and endotoxin from the working environment. The aim of this study was to obtain knowledge about whether serum levels of the markers of systemic inflammation, C-reactive protein (CRP) and serum amyloid A (SAA), are associated with personal exposure to endotoxin, measured using the Limulus (endotoxin_Limulus) and the rFC (endotoxin_rFC) assays, as well as bacteria and fungi in a cohort of WWTP workers. Exposure and blood samples were collected for 11 workers over one year. Exposure to endotoxin_Limulus-day and endotoxin_rFC-day correlated significantly (r = 0.80, p<0.0001, n = 104), but endotoxin_Limulus-day was 4.4 (Geometric mean (GM) value) times higher than endotoxin_rFC-day (p<0.0001). The endotoxin_Limulus-day, endotoxin_rFC-day, bacteria, and fungal exposure as well as serum levels of CRP_-day (GM=1.4 mg/l) and SAA_-day (GM=12 mg/l) differed between workers. Serum levels of SAA_day correlated significantly with CRP_day (r = 0.30, p = 0.0068). The serum levels of CRP_day were associated significantly with exposure to endotoxin_Limulus-day. Exposure, SAA and CRP data were also analyzed as av. of each season, and SAA_season was associated positively and significantly with endotoxin_{Limulus-season} and endotoxin_rFC-season and negatively with fungal_season exposure. In conclusion, CRP_day was associated with the endotoxin_Limulus-day and SAA_season with endotoxin_{Limulus-season} and endotoxin_rFC-season exposure. Thus, we hereby document that WWTP workers are exposed to airborne endotoxin which seems to have a negative impact on their health.

Potential Exposure to Respiratory and Enteric Bacterial Pathogens among Wastewater Treatment Plant Workers, South Africa

Wastewater handling has been associated with an increased risk of developing adverse health effects, including respiratory and gastrointestinal illnesses. However, there is a paucity of information in the literature, and occupational health risks are not well quantified. Grab influent samples were analysed using Illumina Miseq 16S amplicon sequencing to assess potential worker exposure to bacterial pathogens occurring in five municipal wastewater treatment plants (WWTPs). The most predominant phyla were Bacteroidota, Campilobacterota, Proteobacteria, Firmicutes, and Desulfobacterota, accounting for 85.4% of the total bacterial community. Taxonomic analysis showed a relatively low diversity of bacterial composition of the predominant genera across all WWTPs, indicating a high degree of bacterial community stability in the influent source. Pathogenic bacterial genera of human health concern included Mycobacterium, Coxiella, Escherichia/Shigella, Arcobacter, Acinetobacter, Streptococcus, Treponema, and Aeromonas. Furthermore, WHO-listed inherently resistant opportunistic bacterial genera were identified. These results suggest that WWTP workers may be occupationally exposed to several bacterial genera classified as hazardous biological agents for humans. Therefore, there is a need for comprehensive risk assessments to ascertain the actual risks and health outcomes among WWTP workers and inform effective intervention strategies to reduce worker exposure.

Risk and Status of Gastrointestinal Cancer According to the International Standard Industrial Classification in Korean Workers

Simple Summary

The risk of developing cancers varies depending on occupation, which is a well-known fact. It is crucial to investigate the risk of developing gastrointestinal (GI) cancer in the entire industry. In this study, we calculated the standardized incidence ratios (SIRs) of GI cancer by all industrial sectors as classified in the Korean Standard Industrial Classification (KSIC). There were noticeable differences among industries in the risk of GI cancer. The SIR of all GI cancer was highest among miners and quarriers, and second highest among transportation workers. These results suggest that further research is required to identify the risk factors present in each industry that contribute to the development of GI cancers. We believe this study can help to create tailored cancer prevention strategies for different industrial sectors.

Abstract

To compare the risk of developing gastrointestinal (GI) cancer according to industrial groups, we performed a retrospective cohort study using the database of the Korea National Health Insurance Service (NHIS). We calculated the age-standardized incidence ratios (SIRs) and 95% confidence intervals (95% CIs) for the types of GI cancers according to the Korean Standard Industrial Classification (KSIC) compared with the whole employee population. The highest SIR for all GI cancer was found in the “Mining and quarrying” section (SIR, 1.30; 95% CI, 1.14–1.47), followed by the “Transportation and storage” section (SIR, 1.27; 95% CI, 1.24–1.30). Miners and quarriers had the highest risk of developing gastric cancer (SIR, 1.29; 95% CI, 1.06–1.55) and cancer of the liver and intrahepatic bile ducts (SIR, 1.48; 95% CI, 1.17–1.86). Transportation workers had the highest SIR of cancer of the lip, oral cavity, and pharynx (SIR, 1.27; 95% CI, 1.13–1.43) and cancers of the rectum, anus, and anal canal (SIR, 1.27; 95% CI, 1.19–1.35). There were distinct GI cancers with an elevated risk in each industry group. Our findings imply that distinct cancer prevention programs should be developed for each industrial sector.

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.

Characteristics and Determinants of the Presence of Respiratory Symptoms among Sewage Workers in Malaysia

Background

The purpose of this study was to determine the relationships of PM 2.5 and H₂S exposure with the presence of work-related respiratory symptoms among sewage workers.

Methods

A cross-sectional study was conducted in eleven sewage plants located in the central region of Peninsular Malaysia. One hundred ninety-one sewage workers were assessed using the British Medical Research Council (BMRC) questionnaire. Area air sampling was performed in three different sewage plants to measure the following parameters: physical air quality and concentration of PM 2.5 and H₂S.

Result

Chronic cough (34.0%) was reported as the most common symptom, followed by chronic phlegm (26.2%), shortness of breath (7.9%), and chest tightness (3.7%). There were five significant determinants of the presence of respiratory symptoms among the sewage workers: shift work (AOR 23.50, 95% CI: 1.90–616.52), working at a sludge treatment facility (STF) (AOR 25.46, 95% CI: 2.06–314.29), a longer duration of working years (AOR 1,21, 95% CI: 1.01–1.44), individual cumulative exposure to PM 2.5 (AOR 9.01, 95% CI: 1.98–83.33), and individual cumulative exposure to H₂S (AOR 1.04, 95% CI: 1.01–1.07). The majority of STF and non-STF workers had higher exposure to PM 2.5 and H₂S concentrations in the air than office workers.

Conclusion

Sewage workers working at non-STFs or STFs reported a significantly higher prevalence of work-related respiratory symptoms and exposure to PM 2.5 and H₂S compared with office workers. Exposure-response relationships were also found in sewage workers' cumulative exposure to PM 2.5 and H₂S and the presence of respiratory symptoms.

Occupational health outcomes among sanitation workers: A systematic review and meta-analysis

BACKGROUND

Sanitation workers are essential to global public health and societal wellbeing. However, the health risks and outcomes associated with exposure to occupational risk factors among sanitation workers are neither well understood nor well quantified. We undertook a systematic review to (1) identify occupational risk factors among sanitation workers and (2) assess the effect of occupational exposure to human fecal sludge and wastewater on selected health outcomes among these workers.

METHODS

We searched four databases (i.e., PubMED, MEDLINE, EMBASE, and LILACS) for eligible studies from inception through to January 01, 2020. The included population was workers ≥15 years engaged, formally or informally, in installing, operating, servicing, cleaning or emptying a sanitation technology at any step of the sanitation chain. The included comparator was workers in other occupations or the general population. Eligible outcomes were: mortality (any or all causes), gastroenteritis, occupational injuries, respiratory diseases, musculoskeletal disorders, and mental and social health conditions. Risk of bias was assessed separately on exposure assessment and health outcome using a modified Liverpool Quality Assessment Tool (LQAT). We pooled sufficiently homogenous studies using inverse variance meta-analysis with random effects.

RESULTS

A total of 65 studies (9 cohort studies, 56 cross-sectional studies) met the inclusion criteria. One quarter of studies (n = 15) were from middle-income countries. Few studies assessed occupational risk factor exposures directly; most assigned exposure via proxy of occupation of sanitation worker. We judged nearly all studies to have "high risk of bias" in exposure and outcome assessment. Despite these limitations, the consistency of the overall evidence suggests that sanitation workers are at increased risk of gastroenteritis and respiratory conditions, and may be at increased risk of musculoskeletal disorders and mental/social health conditions. The pooled odds ratio for hepatitis A--the only outcome deemed suitable for meta-analysis--was 2.09 (95% Predicted Interval: 1.39-3.00, 12 studies). There was conflicting evidence from studies of increased risk of mortality; only one study reported on injuries.

CONCLUSION

Despite a large number of studies, there is limited evidence to date of the health risks faced by sanitation workers, particularly among groups that may be at particular risk-- women, informal workers and those living in low-income countries. Nevertheless, the research to date provides suggestive evidence of elevated occupational risk among sanitation workers across a range of health condition. More research is needed to improve the current bodies of evidence for all included health outcomes to be able to quantify disease burden among this occupational group.

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 β = 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 (β = 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.

Systematic Review of Potential Occupational Respiratory Hazards Exposure Among Sewage Workers

Background: Sewage workers have a higher risk of exposure to various potential occupational respiratory hazards found in sewage plants. Although previous studies discuss occupational respiratory hazard concentration impacting sewage workers' respiratory health, the results are scarce and mixed. Hence, there is a need to identify the potential respiratory hazards in sewage plants so as to clarify the short- and long-term respiratory health effects. Therefore, this systematic review (SR) aims to critically review previous studies investigating potential respiratory hazards found at sewage plants and their effects on sewage workers' respiratory health. Methods: An SR was conducted using PubMed, EBSCO Medline, Web of Science, Scopus, and Google Scholar on peer-reviewed studies published between January 1994 and October 2020 evaluating the impact of potential exposure to respiratory hazards and its effects on respiratory health among sewage workers. "Sewage treatment plant," "respiratory hazards," and "respiratory health effects" were the three main search terms chosen in this SR. The inclusion criteria were (1) studies on potential occupational respiratory hazard exposure among sewage workers, (2) manuscripts written in English, and (3) studies published in the peer-reviewed literature. The human observational studies' quality was assessed using the Effective Public Health Practice Project Quality Assessment Tool. Results: We identified 5,660 articles through an initial database search. Only 26 items met the inclusion criteria and were included in this review; 15 human observational studies and 11 environmental assessment studies were conducted in the sewage industries. Most of the human observational studies were rated as moderate quality, two studies were rated as weak quality, and one study with strong quality was identified. Hydrogen sulfide, bioaerosols, particulate matter 2.5 (PM 2.5), and volatile organic compounds (VOC) were found to be potential respiratory hazards. Most of the risks contributed to adverse outcomes on the sewage workers' respiratory health with some inconsistent findings on the relationship between respiratory hazard exposure and respiratory health effects. Conclusion: Our review finds that, although this area is of great importance, quality studies are still lacking. There is a need for additional studies to clarify the effects of respiratory hazard exposure on sewage workers and respiratory health, especially PM 2.5 and VOC.

A cohort study of cucumber greenhouse workers' exposure to microorganisms as measured using NGS and MALDI-TOF MS and biomarkers of systemic inflammation

Work in greenhouses entails exposure to airborne fungi and bacteria. The aims of this study are to obtain knowledge about whether exposure to fungal and bacterial genera and species during work in a cucumber greenhouse is affected by work tasks, and whether a cohort of greenhouse workers' serum levels of serum amyloid A (SAA) and C-reactive protein (CRP), biomarkers of systemic inflammation, are associated with this. Data on personal exposure to airborne fungal and bacterial species measured over 4 years as well as serum levels of SAA and CRP sampled over two years were analyzed. For data analysis, the main work tasks were grouped into three different groups, called 'grouped work task'. Microorganisms were identified using matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF MS) and next-generation sequencing (NGS). The 'daily exposure' of greenhouse workers' were as follows: 4.8 × 10⁴ CFU bacteria/m³, 1.4 × 10⁶ CFU fungi/m³, and 392 EU/m³ of endotoxin. Workers were exposed to many different microbial species including several species within the genera Acinetobacter, Bacillus, Microbacterium, Pseudomonas, Staphylococcus, and Streptomyces. The genera Ralstonia and Cladosporium were found in most samples. The exposure levels as well as the microbial composition were associated significantly with grouped work task and season with high exposures during tasks in close contact with mature and old plants and in the autumn. CRP and SAA levels were also associated with exposure level and grouped work tasks. The Shannon-Wiener indices were not different in the 3 'grouped work tasks'. Several specific species including e.g. Halomonas elongata, Stenotrophomonas maltophilia, Podosphaera fusca, and Wallemia spp. were found frequently or in high concentrations in the exposures associated with the highest levels of CRP and SAA. The microorganisms S. maltophilia, P. fusca, and Wallemia spp. were also found on the cucumber plant leaves. In conclusion, both exposure level and the species composition seem to have an effect on the serum levels of CRP and SAA of exposed workers. The greenhouse workers were exposed to only a few species characterized as human pathogens.

Occupational exposure during treatment of offshore drilling waste and characterization of microbiological diversity

The exposure for workers handling and recycling offshore drilling waste are previously not described, and given the potential for exposure to hazardous components, there is a need for characterizing this occupational exposure. In this study five plants recycling offshore drilling waste with different techniques were included. Measurements were conducted in both winter and summer to include seasonal exposure variations. Altogether >200 personal air-exposure measurements for oil mist, oil vapor, volatile organic compounds (VOC), hydrogen sulfide (H₂S) and solvents were carried out respectively. Microorganisms related to drilling waste were identified in bulk samples and in stationary air measurements from two of the plants. The exposure to oil mist and oil vapor were below 10% of the current Norwegian occupational exposure limits (OEL) for all measured components. The plants using the Resoil or TCC method had a statistically significant higher exposure to oil vapor than the plant using complete combustion (p-value <0.05). No statistically significant difference was found between the different treatment methods for oil mist. The exposure to solvents was generally low (additive factor < 0.03). Endotoxin measurements done during winter showed a median concentration of 5.4 endotoxin units (EU)/m³. Levels of H₂S above the odor threshold of 0.1 ppm were measured at four plants. Both drill mud and slop water contained a high number and diversity of bacteria (2-4 × 10⁴ colony forming unit (CFU)/mL), where a large fraction was Gram-negative species. Some of the identified microorganisms are classified as potentially infectious pathogens for humans and thus might be a hazard to workers.