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.

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.

Cross-shift study of exposure-response relationships between bioaerosol exposure and respiratory effects in the Norwegian grain and animal feed production industry.

OBJECTIVE: We have studied cross-shift respiratory responses of several individual bioaerosol components of the dust in the grain and feed industry in Norway. METHODS: Cross-shift changes in lung function and nasal congestion, as well as in respiratory and systemic symptoms of 56 exposed workers and 36 referents, were recorded on the same day as full-shift exposure to the inhalable aerosol fraction was assessed. Exposure-response associations were investigated by regression analysis. RESULTS: The workers were exposed on average to 1.0 mg/m(3) of grain dust, 440 EU/m(3) of endotoxin, 6 µg/m(3) of ß-1,3-glucans, 17×10(4)/m(3) of bacteria and 4×10(4)/m(3) of fungal spores during work. The exposure was associated with higher prevalence of self-reported eye and airway symptoms, which were related to the individual microbial components in a complex manner. Fatigue and nose symptoms were strongest associated with fungal spores, cough with or without phlegm was associated with grain dust and fungal spores equally strong and wheeze/tight chest/dyspnoea was strongest associated with grain dust. Bioaerosol exposure did not lead to cross-shift lung function decline, but several microbial components had influence on nose congestion. CONCLUSIONS: Exposure to fungal spores and dust showed stronger associations with respiratory symptoms and fatigue than endotoxin exposure. The associations with dust suggest that there are other components in dust than the ones studied that induce these effects.

Biomarkers of inflammation in workers exposed to compost and sewage dust.

PURPOSE: The association between exposure during handling of sewage and compost and the serum concentration of inflammatory biomarkers was studied. METHODS: A total of 44 workers exposed to sewage dust, 47 workers exposed to compost dust and 38 referents from the administrative staff participated. Microbial aerosols were collected by personal inhalable samplers. The concentrations of bacterial cells, spores from fungi and bacteria (actinomycetes) and endotoxins were determined by fluorescence and scanning electron microscopy and the Limulus assay. Fibrinogen, D-dimer, ICAM-1, VCAM-1 and IL-6 were determined by ELISA and C-reactive protein (CRP) by HS-MicroCRP assay in blood samples collected post-shift. RESULTS: The exposure to dust ranged from 0.02 to 11 mg/m(3), endotoxins from 1 to 3160 EU/m(3) and bacteria from 0 to 209 × 10(6) cells/m(3). Fungal (0-41 × 10(6) spores/m(3)) and actinomycetes spores (0-590 × 10(6) actinomycetes spores/m(3)) were observed only at compost plants. The exposed workers had significantly higher fibrinogen (arithmetic mean 3.3 mg/ml) and CRP (geometric mean 1.5 mg/L) compared to the referents (2.8 and 1.0 mg/L, respectively). The serum concentration of CRP was negatively associated with forced expiratory volume in one second (FEV1) in  % of predicted. Exposure to inhalable dust and bacteria was positively associated with the serum concentration of ICAM-1. CONCLUSIONS: This study suggests that exposure to bacteria and dust when handling sewage and compost may initiate an inflammation shown by an increase in serum concentration of ICAM-1. The higher concentrations of fibrinogen and CRP in exposed workers compared to the referents may reflect a low-grade systemic inflammation.

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.

Work Tasks as Determinants of Grain Dust and Microbial Exposure in the Norwegian Grain and Compound Feed Industry.

OBJECTIVES: The grain and compound feed industry entails inevitable risks of exposure to grain dust and its microbial content. The objective of this study was therefore to investigate task-dependent exposure differences in order to create knowledge basis for awareness and exposure reducing measures in the Norwegian grain and compound feed industry. METHODS: A total of 166 samples of airborne dust were collected by full-shift personal sampling during work in 20 grain elevators and compound feed mills during one autumn season and two winter seasons. The personal exposure to grain dust, endotoxins, ß-1→3-glucans, bacteria, and fungal spores was quantified and used as individual outcomes in mixed models with worker nested in company as random effect and different departments and tasks as fixed effects. RESULTS: The exposure levels were highest in grain elevator departments. Exposure to endotoxins was particularly high. Tasks that represented the highest and lowest exposures varied depending on the bioaerosol component. The most important determinants for elevated dust exposure were cleaning and process controlling. Cleaning increased the dust exposure level by a factor of 2.44 of the reference, from 0.65 to 1.58mg m(-3), whereas process controlling increased the dust exposure level by a factor of 2.97, from 0.65 to 1.93mg m(-3). Process controlling was associated with significantly less grain dust exposure in compound feed mills and the combined grain elevators and compound feed mills, than in grain elevators. The exposure was reduced by a factor of 0.18 and 0.22, from 1.93 to 0.34mg m(-3) and to 0.42mg m(-3), respectively, compared with the grain elevators. Inspection/maintenance, cleaning, and grain rotation and emptying were determinants of higher exposure to both endotoxin and ß-1→3-glucans. Seed winnowing was in addition a strong determinant for endotoxin, whereas mixing of animal feed implied higher ß-1→3-glucan exposure. Cleaning was the only task that contributed significantly to higher exposure to bacteria and fungal spores. CONCLUSION: Cleaning in all companies and process controlling in grain elevators were the strongest determinants for overall exposure, whereas seed winnowing was a particular strong determinant of endotoxin exposure. Exposure reduction by technical intervention or personal protective equipment should therefore be considered at work places with identified high exposure tasks.

Respiratory effects of bioaerosols: exposure-response study among salmon-processing workers.

OBJECTIVES: The aim of the study was to determine exposure-response relationships in salmon-processing workers. METHODS: Cross-shift FEV1, acute respiratory symptoms, and exposure to total protein, parvalbumin and endotoxin were main variables measured during one workweek. Exposure-response relationships were analyzed by Generalized Estimation Equations of cross-week data and by multiple regressions of day-to-day data. RESULTS: Exposure levels were higher in those workers who reported use of water hose. GEE showed negative coefficients for interaction between TP exposure and time (days) on cross-week change of FEV1. Multiple regressions showed significant associations between TP levels and cross-shift change of FEV1 and symptoms (cough, chest tightness) only for Monday shifts. CONCLUSIONS: A tolerance effect during the course of a workweek is suggested. Use of water hose is a risk process with regard to the liberation of measured components of bioaerosols.

Exposure to grain dust and microbial components in the Norwegian grain and compound feed industry.

OBJECTIVES: The aim of this study was to extensively characterize grain workers' personal exposure during work in Norwegian grain elevators and compound feed mills, to identify differences in exposures between the workplaces and seasons, and to study the correlations between different microbial components. METHODS: Samples of airborne dust (n = 166) were collected by full-shift personal sampling during work in 20 grain elevators and compound feed mills during one autumn season and two winter seasons. The personal exposure to grain dust, endotoxins, ß-1→3-glucans, bacteria, and fungal spores was quantified. Correlations between dust and microbial components and differences between workplaces and seasons were investigated. Determinants of endotoxin and ß-1→3-glucan exposure were evaluated by linear mixed-effect regression modeling. RESULTS: The workers were exposed to an overall geometric mean of 1.0mg m(-3) inhalable grain dust [geometric standard deviation (GSD) = 3.7], 628 endotoxin units m(-3) (GSD = 5.9), 7.4 µg m(-3) of ß-1→3-glucan (GSD = 5.6), 21 × 10(4) bacteria m(-3) (GSD = 7.9) and 3.6 × 10(4) fungal spores m(-3) (GSD = 3.4). The grain dust exposure levels were similar across workplaces and seasons, but the microbial content of the grain dust varied substantially between workplaces. Exposure levels of all microbial components were significantly higher in grain elevators compared with all other workplaces. The grain dust exposure was significantly correlated (Pearson's r) with endotoxin (rp = 0.65), ß-1→3-glucan (rp = 0.72), bacteria (rp = 0.44) and fungal spore (rp = 0.48) exposure, whereas the explained variances were strongly dependent on the workplace. Bacteria, grain dust, and workplace were important determinants for endotoxin exposure, whereas fungal spores, grain dust, and workplace were important determinants for ß-1→3-glucan exposure. CONCLUSIONS: Although the workers were exposed to a relatively low mean dust level, the microbial exposure was high. Furthermore, the exposure levels of microbial components varied between workplaces although the dust levels were similar. We therefore recommend that exposure levels at different workplaces should be assessed separately and a task-based assessment should be done for detailed evaluation of efficient dust-reducing measures. The microbial content and knowledge of health effects of the microbial components should be considered in health risk evaluations of these workplaces.

Pneumoproteins in sewage workers exposed to sewage dust.

PURPOSE: The association between exposure to bacteria and endotoxins in sewage dust and the serum concentrations of pneumoproteins in sewage treatment plant workers were studied. METHODS: Forty-four workers from eight sewage treatment plants and 38 reference workers participated in the study. Microbial aerosol was collected by personal inhalable samplers. The concentrations of bacteria and endotoxins were determined by fluorescence microscopy and the Limulus assay, respectively. Pneumoproteins (Clara cell protein: CC16, and Surfactant proteins A and D: SP-A, SP-D) were determined by ELISA in blood samples collected post-shift. RESULTS: The exposure to dust ranged from 0.02 to 9.3 (geometric mean (GM) 0.3 mg/m(3), of bacteria from 0.3 to 4,900 × 10(3) (GM 27 × 10(3)) cells/m(3) and endotoxins from 1 to 3,160 (GM 28) EU/m(3). The exposed workers had lower CC16 [arithmetic mean (AM) 4.9 ng/ml] compared to the referents (AM 6.4 ng/ml, p < 0.01). No significant difference was observed for SP-D and SP-A. Exposure to bacteria was positively associated with CC16 (p < 0.05) and SP-D (p < 0.05), adjusting for possible confounders. CONCLUSIONS: This study showed that exposed workers had lower serum concentration of CC16 as compared to the referents, which may reflect a long-term effect on secretion of these pneumoproteins. The positive association between exposure to bacteria and the serum concentrations of CC16 and SP-D may be explained by a transient increased permeability of the lung-blood barrier.

Long-term occupational outcomes of endotoxin exposure and the effect of exposure cessation.

OBJECTIVE: To study the possible respiratory and haematological effects of endotoxin exposure to bacterial single-cell protein (BSCP) in workers during a follow-up period of 5 years including 4 years of exposure and 1 year without exposure. METHODS: The study included 28 workers examined in 2002-2005 and 1 year after exposure termination in 2007. The arithmetic mean endotoxin exposure was 5800-11,000 EU/m(3) among the high exposure group and 390 EU/m(3) in the low exposure group. Assessment of lung function included spirometry and gas diffusion in 2003, 2004 and 2007. Rhinometry was performed in 2004 and 2007. Blood analysis included leukocyte cell count and measurement of the acute phase proteins: C-reactive protein, interleukin-6, eosinophilic cationic protein, macrophage inflammatory protein-1α, monocyte chemoattractant protein-1, chemoattractant protein RANTES, platelet-derived growth factor BB, fibrinogen and D-dimer. RESULTS: In the low exposure group, but not in the high exposure group, there were significant improvements in both forced vital capacity (FVC) (290 ml) and forced expiratory volume in 1 s (FEV(1)) (180-210 ml) (p=0.004-0.03) 1 year after the end of exposure. The number of leukocytes and eosinophilic cationic protein and D-dimer levels increased significantly with increasing endotoxin exposures and decreased significantly 1 year after exposure termination. Changes in acute phase proteins suggested exposure-related tolerance. CONCLUSIONS: An inflammatory tendency during an exposure period of 4 years seems to reverse 1 year after cessation of exposure to endotoxins from a single species. Lung function improved significantly among workers exposed to low levels of endotoxin but not among the highly exposed workers.

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.

Associations between acute symptoms and bioaerosol exposure during the collection of household waste.

BACKGROUND: A study was performed to investigate associations between work-related symptoms and bioaerosol exposure in 22 workers collecting waste separated at source and mixed household waste. METHODS: Full work shift exposures to bacteria (spherical and rod-shaped) fungal spores, endotoxins, and total dust were measured. Symptoms experienced during work on the day that exposure was measured were recorded by use of a short questionnaire. Questions were posed on respiratory symptoms, systemic effects such as headache, tiredness, and gastrointestinal symptoms. RESULTS: The median exposure levels of bacteria and fungal spores were 0.4 and 0.1 x 10(6)/m3, respectively. The exposure to rod-shaped bacteria (7% of the bacteria count), endotoxins (1.8 EU/m3), and dust (0.2 mg/m3) was low. The symptoms most often reported were unusual tiredness (24%), headache (22%), cough (15%), and irritation in eyes and nose (10 and 17%). These symptoms were also found to be associated to microbial components. CONCLUSIONS: The results suggest that acute work-related nose irritation is associated with exposure to bacteria. Rod-shaped bacteria were also associated with nose irritation and unusual tiredness. It is likely that cough is associated to fungal spores, while other associations which were found could be due to confounding.