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Assessment of Occupational Exposure Risks to Sewage Workers

Cowie, C*; Driscoll, T*; Armstrong, B*; Foster, G; Priestly, B; Deere, D§; Nossar, G; Jalaludin, B

ISEE/ISEA 2006 Conference Abstracts Supplement: Symposium Abstracts: Abstracts

*SPH, The University of Sydney, Sydney. †Foster OHS Services, Sydney. ‡Monash University, Melbourne. §Water Futures, Sydney. ¶Royal Prince Alfred Hospital, Sydney. ∥University of NSW, Sydney.


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A study was commissioned following concerns expressed by sewage workers from a major sewage utility over exposure to chemical substances through their daily work. The study involved a literature review, site visits and a health risk assessment of occupational exposure to chemical and microbiological substances in sewage.

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A review of relevant literature accessed through PubMed, Oshrom, the sewage utility and the World Wide Web was conducted. A series of 29 site visits and an exposure assessment workshop were conducted to provide information on the actual duration and extent of exposures associated with different job tasks. The above activities collected considerable information for use in the health risk assessments. The degree of quantitative analysis conducted for the risk assessment largely relied on the ability to assign exposure values for contaminants to the sewer workers. In many instances, there was a paucity of data, however, for all scenarios we incorporated conservative estimates for the exposures.

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Results and Discussion:

With a few exceptions, the epidemiological studies that have examined the effect of chemical exposure in sewer workers have generally found equivocal evidence of adverse health effects. Results of studies investigating microbiological exposures are also limited given that many have not adequately addressed potential confounders or did not assess the vaccination status of participants (hepatitis A). However, it is clear that sewage workers are occasionally exposed to significant levels of hazardous substances. The microbial risk assessment predicted that sewer workers would be expected to become symptomatically ill due to their work at a frequency of approximately once every one to three years. The risk assessment result is not surprising, given the exposures involved. The chemical risk assessment found that the quantitative risk estimates for chemical exposures from inhalational, oral and dermal exposures are in most cases an order of magnitude lower than the value which is considered to represent a safe level of exposure. The main exception to this finding was in relation to inhalational exposure to sulphides. Observations made during the site visits and discussions with workers revealed a number of areas for potential improvement in work practices. Accordingly, the study findings made recommendations relating primarily to health and safety practices, vaccination for hepatitis A and B, the potential for increased environmental monitoring and improving dissemination of information to workers.

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