Wastewater workers and hepatitis A virus infection

Department of Preventive Medical Sciences, Medical School, University 'Federico II', Naples, Italy.
Occupational Medicine (Impact Factor: 1.03). 06/2009; 59(7):506-8. DOI: 10.1093/occmed/kqp092
Source: PubMed


The main occupational hazard of wastewater workers (WWs) is the direct exposure to the variety of infectious agents present in sewage material, with hepatitis A virus (HAV) being the most frequent one. Most epidemiological studies have shown a higher risk of hepatitis A among WWs, although some studies have produced conflicting evidence.
To evaluate the hypothesis of increased risk of HAV infection in WWs.
The prevalence of antibodies to HAV in 869 WWs was compared to 311 other subjects and analysed to detect the main potentially confounding variables.
Univariate analysis demonstrated that occupational exposure to sewage was not significantly associated with the prevalence of anti-HAV(+). The anti-HAV(+) prevalence was strongly associated with age and shellfish consumption (P < 0.05) when the subcategories of workers were examined separately (WWs and control group) and jointly. In the logistic regression model, a significant association between anti-HAV(+) prevalence and duration of employment (P < 0.05) was found. The interaction term (age x duration of employment) was significant (P < 0.001) when included in the logistic model.
This study shows that working in a wastewater treatment plant does not seem to be related to a greater prevalence of antibodies to hepatitis A. Moreover, the relative risk of HAV infection among WWs seems to be correlated with low anti-HAV(+) prevalence in the general population.

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    ABSTRACT: Raw sewage ordinarily contains various biohazards (disease-causing organisms and their products), such as bacteria, viruses, fungi, helminths, and protozoa. Types, concentrations and survival of biohazards in sewage vary greatly depending on geographical and seasonal factors, and treatment levels within a wastewater treatment plant (WWTP). A review was undertaken to identify evidence of biohazard exposures and health symptom responses in WWTP workers who may be at increased occupational risk compared to the general population. Studies from 1990 onwards identified the following WWTP equipment or tasks as the most important for biohazard exposures: pre-treatment equipment (either indoors or in confined areas), sludge dewatering equipment, worker tasks involving water used for cleaning and contact with raw sewage. Twenty-eight epidemiological observational studies were identified that compared various markers of biohazard exposure and/or health symptom responses in WWTP worker cohorts and non-worker cohorts for potential exposure to bacteria, viruses, molds and/or endotoxin. Most epidemiological studies comparing self-reported and/or actual health symptoms of WWTP workers to those of non-exposed controls do not show evidence of causality of health symptoms and/or biomarkers of biohazards commonly found in sewage and/or their findings indicate that occupational health risks to WWTP workers are small. Instances where evidence of causality is suggested tend to be based on self-reported outcomes. Caution is acknowledged in interpreting studies suggesting causality of self-reported symptoms because these studies can be influenced by awareness bias of subjects. Equipment, processes and work tasks associated with bioaerosol emissions and worker exposure controls at WWTPs are also discussed.
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