A cross-sectional study of sensory-motor neuropsychological function among sewage plant and sewage net workers exposed to hydrogen sulphide when handling wastewater.

OBJECTIVES: Workers at sewage treatment plants are exposed to a complex mixture of toxins, including hydrogen sulphide (H2S). An issue of concern among sewage workers, is possible negative nervous system effects from low-level H2S exposure. Empirical neuropsychological evidence indicates both that low-dose exposure to H2S exposure affects the nervous system, and the contrary, that such exposure may facilitate nervous system function, since H2S is an endogenously produced central nervous system (CNS) gasotransmitter. The aim of this study is to describe a possible association between the H2S component of the total exposure and long-term effects on neuropsychological motor function among wastewater workers. METHODS: Workers (N = 138) treating wastewater in 6 sewage-treatment plants, or in the sewer net system participated in a cross-sectional study. H2S exposure was expressed in a dichotomous exposure variable defining currently H2S-exposed (N = 112) and unexposed referent workers (N = 26), and a variable defining a job-exposure matrix for long-term total typical workplace H2S exposure. The participants went through neuropsychological tests for hand coordination, reaction time (SRT), and balance, and completed questionnaires. Pearson chi-square test or independent samples t-test was used when comparing the currently H2S-exposed workers with the unexposed control group. Multiple linear regression was used to assess associations between the independent variables age, smoking and exposure variables, and the neuropsychological tests. RESULTS: The analyses indicate increased SRT in the currently H2S-exposed group compared to controls (mean [SD] = 225.8 [29.9] versus 210.7 [26.3] ms, P = 0.019), and an association between increased SRT and current H2S-exposure in the total study sample (ß = 14.7, P = 0.026, R2 = 0.06, P = 0.050). Blindfolded balance testing indicates a nonsignificant trend in the total study sample, of reduced balance in the highest versus lowest H2S total long-term exposure-index group (Sway area [mean {SD}, mm2: 702 [410] versus 581 [278]), and a significant association between total long-term H2S exposure and reduced balance among smokers (Sway area, mm2 [ß = 38.7, P = 0.039], mean sway, mm [ß = 0.3, P = 0.015]). CONCLUSION: The observed trends and associations may be due to exposure peaks in certain work operations and pinpoint the importance of minimizing and avoiding exposure peaks, also when H2S time-weighted average measurements do not exceed an occupational exposure limit of 5 ppm.

Profiling of 3-hydroxy fatty acids as environmental markers of endotoxin using liquid chromatography coupled to tandem mass spectrometry.

3-Hydroxy acids are constituents of the lipid A part of lipopolysaccharides and may potentially be used as chemical markers of endotoxin. While commercial enzymatic assays, such as the widely used Limulus amebocyte lysate (LAL) assay, commonly detect merely the water-soluble fraction of the bioactive endotoxin, the chemical approach aims to estimate the total amount of endotoxin present in a sample. Our objective was to develop a simple method for quantitative profiling of 3-hydroxy fatty acids in occupational and environmental samples based on detection with HPLC-MS/MS. We included eleven 3-hydroxy fatty acids (3-hydroxyoctanoic acid to 3-hydroxyoctadecanoic acid) in the HPLC-MS/MS based method, which involved base hydrolysis of filter samples using 1M sodium hydroxide and removal of the base as well as concentration of the fatty acids using solid-phase extraction on a functionalized polystyrene-divinylbenzene polymer. Recovery trials from spiked glass fiber filters, using threo-9,10-dihydroxyhexadecanoic acid as internal standard, gave an overall recovery of 54-86% for 3-hydroxy fatty acids of medium chain length (3-hydroxynonanoic to 3-hydroxypentadecanoic acid). 3-Hydroxyoctanoic acid and the longer chain fatty acids were more problematic yielding overall spike recoveries of 11-39%. While the 3-hydroxy fatty acid profile of pure lipopolysaccharides was dominated by 3-hydroxydecanoic, 3-hydroxydodecanoic and 3-hydroxytetradecanoic acid the aqueous phase from drilling mud contained in addition relatively high amounts of 3-hydroxyoctanoic and 3-hydroxynonanoic acid. Endotoxin activity as measured by the LAL assay was reasonably correlated (R(2)=0.54) to the sum of 3-hydroxydecanoic acid, 3-hydroxydodecanoic acid and 3-hydroxytetradecanoic acid in these samples.

Airway inflammation among compost workers exposed to actinomycetes spores.

OBJECTIVES: To study the associations between exposure to bioaerosols and work-related symptoms, lung function and biomarkers of airway inflammation in compost workers. MATERIALS AND METHOD: Personal full-shift exposure measurements were performed on 47 workers employed at five windrow plants (n=20) and five reactor plants (n=27). Samples were analyzed for endotoxins, bacteria, fungal and actinomycetes spores. Health examinations were performed on workers and 37 controls before and after work on the day exposure was measured. The examinations included symptoms recorded by questionnaire, lung function by spirometry and nasal dimensions by acoustic rhinometry (AR). The pneumoproteins CC16, SP-D and SP-A were measured in a blood sample drawn at the end of the day. RESULTS: The levels of endotoxins (median 3 EU/m(3), range 0-730 EU/m(3)) and actinomycetes spores (median 0.2 × 10(6) spores/m(3), range 0-590 × 10(6) spores/m(3)) were significantly higher in reactor plants compared to windrow plants. However, windrow composting workers reported more symptoms than reactor composting workers, probably due to use of respiratory protection. Exposure-response relationships between actinomycetes spores exposure and respiratory effects, found as cough and nose irritation during a shift, was significantly increased (OR 4.3, 95% CI 1.1-16, OR 6.1, 95% CI 1.5-25, respectively, p<0.05) among workers exposed to 0.02-0.3 × 10(6) actinomycetes spores/m3, and FEV1/FVC% decreased cross shift (b=-3.2, SE=1.5%, p<0.01). Effects were weaker in the highest exposed group, but these workers used respiratory protection, frequently limiting their actual exposure. No relationships were found between exposure and pneumoprotein concentrations. CONCLUSIONS: The major agent in the aerosol generated at compost plants was actinomycetes spores which was associated with work related cough symptoms and work-shift lung function decrease.

Exposure, symptoms and airway inflammation among sewage workers.

The purpose of the study was to determine the associations between dust, endotoxins and bacterial exposure, and health effects in sewage workers. Exposure of 19 workers handling dry sludge and 25 other sewage workers was measured. Controls were office workers from compost and sewage plants. Spirometry, acoustic rhinometry and nitric oxide in exhaled air were performed before and after exposure were measured. CRP was measured in blood samples. It was found that workers handling dry sludge were exposed to higher levels of dust and endotoxins than other workers and reported more airway and systemic symptoms than controls. Compared to controls, FEV(1)/FVC was 0.12 lower in workers handling dry sludge and 0.05 lower in other sewage workers. Nose irritation, cough and headache were more prevalent in workers handling dry sludge (ORs 2.3-23), and together with unusual tiredness associated with endotoxins and/or dust, ORs 2.9-34 for-10-fold increases in exposure. Cross-shift decreases of nasal dimensions were larger in workers handling dry sludge than controls and were associated with dust and endotoxin exposure. It was concluded that workers handling dry sludge were higher exposed to endotoxins and dust than other sewage workers and also reported more respiratory and systemic symptoms. Exposure-response relationships were found for nasal dimensions, nose irritation and systemic symptoms.