Enzyme measurements for risk evaluations in sewage treatment plants


Objectives: Work in sewage treatment plants may cause health problems in terms of airways symptoms, unusual tiredness, fever, and diarrhoea. The presence of such symptoms has been related to bacterial endotoxin. The project was undertaken to assess if risk evaluations could be performed by measuring the amounts of two different microbial enzymes and to evaluate their relation to endotoxin. Methods: Measurements were performed at 120 work sites in 10 different sewage treatment plants of varying age and capacity. The content of N-acetyl-hexosaminidase (NAHA), bacterial hydrolase (BH) and endotoxin was measured in sewage water and in airborne samples. Results: There was a close relationship between endotoxin and NAHA, both in the water itself and in air samples. Generally exposure levels were low but higher at work sites where the water or sludge was agitated or when repairing pumps and cleaning basins. Conclusions: Measurements of NAHA are suitable to determine risk exposures in sewage treatment plants. Such measurements are faster and cheaper than measures of endotoxin. A level of 50-70 U/m3 is suggested as a risk threshold. Further work is required to define more precise threshold limit values.

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Rylander, R. and Calo, A. (2012) Enzyme measurements for risk evaluations in sewage treatment plants. Open Journal of Preventive Medicine, 2, 339-343. doi: 10.4236/ojpm.2012.23049.

Conflicts of Interest

The authors declare no conflicts of interest.


[1] Anders, W. (1954) Die berliner kanalbetriebsarbeiter. Medical Microbiology and Immunology, 139, 341-371. doi:10.1007/BF02152578
[2] Mattsby, I. and Rylander, R. (1978) Clinical and immu- nological findings in workers exposed to sewage dust. Journal of Occupational and Environmental Medicine, 20, 690-692.
[3] Nethercott, J.R. and Holness, D.L. (1988) Health status of a group of sewage treatment workers in Toronto, Canada. American Industrial Hygiene Association Journal, 49, 346-350. doi:10.1080/15298668891379873
[4] Rylander, R. (1999) Health effects among workers in sewage treatment plants. Occupational and Environmental Medicine, 56, 354-357. doi:10.1136/oem.56.5.354
[5] Thorn, J., Beijer, L. and Rylander, R. (2002) Work-related symp-toms among sewage workers, a nationwide survey in Sweden. Occupational and Environmental, 59, 562-566. doi:10.1136/oem.59.8.562
[6] Heidal, K.K., Mads?, L., Huser, P.O., et al. (2010) Exposure, symptoms and air-way inflammation among sewage workers. Annals of Agricultural and Environmental Medicine, 17, 263-268.
[7] Laitinen, S., Kangas, J., Kotimaa, M., et al. (1994) Workers’ exposure to airborne bacteria and en-dotoxin at industrial wastewater treatment plants. American Industrial Hygiene Association Journal, 55, 1055-1060. doi:10.1080/15428119491018330
[8] Pra?mo, Z., Krysinska-Traczyk, E., Skórska, C., et al. (2003) Exposure to bioaerosols in a municipal sewage treatment plant. Annals of Agricultural and Environmental Medicine, 10, 241-248.
[9] Korzeniewska, E. (2011) Emission of bacteria and fungi in the air from wastewater treatment plants—A review. Frontiers in Bioscience, 3, 393-407. doi:10.2741/s159
[10] Rylander, R. (2007) Endotoxin in the air—Good or bad for you? Clinical Pulmonary Medicine, 14, 140-147. doi:10.1097/CPM.0b013e3180557041
[11] Thorn, J. and Beijer, L. (2004) Work-related symptoms and inflammation among sewage plant operatives. International Journal of Occupational and Environmental Health, 10, 84-89.
[12] Thorn, J., Beijer, L., Jonsson, T., et al. (2002) Measurements strategies for the determination of airborne bacte- rial endotoxin in sewage treatment plants. Annals of Occupational Hygiene, 46, 549-554. doi:10.1093/annhyg/mef068
[13] Smit, L.A.M., Spaan, S. and Heederik, D. (2005) Endo- toxin exposure and symptoms in wastewater treatment workers. American Journal of Industrial Medicine, 48, 30-39. doi:10.1002/ajim.20176
[14] Chun, D.T.W., Chew, V., Bartlett, K., et al. (2002) Second inter-laboratory study comparing endotoxin assay results from cotton dust. Annals of Agricultural and Environmental Medicine, 9, 49-53.
[15] Miller, M., Paloj?rvi, A., Rangger, A. Reeslev, M. and Kj?ller, A. (1998) The use of fluorogenic substrates to measure fungal presence and activity in soil. Applied and Environmental Microbiology, 64, 613-617.
[16] Madsen, A.M. (2003) NAGase activity in airborne biomass dust and relationship between NAGase concentration and fungal spores. Aerobiologia, 19, 97-105. doi:10.1023/A:1024401523656
[17] Rylander, R., Reeslev, M. and Hulander, T. (2010) Air- borne enzyme measurements to detect indoor mould exposure. Journal of Environmental Monitoring, 12, 2161- 2164. doi:10.1039/c0em00336k
[18] Douwes, J., Mannetje, A. and Heederik, D. (2001) Work- related symptoms in sewage treatment workers. Annals of Agricultural and Environmental Medicine, 8, 39-45.
[19] Liebers, V., Brüning, T., Raulf-Heimsoth, M. (2006) Occupational endotoxin-exposure and possible health effects on humans. American Journal of Industrial Medicine, 49, 474-491. doi:10.1002/ajim.20310
[20] Sandstr?m, T., Bjermer, L. and Rylander, R. (1992) Lipo- polysaccharide (LPS) inhalation in healthy subjects increases neutrophils, lymphocytes and fibronectin levels in bronchoalveolar lavage fluid. European Respiratory Journal, 5, 992-996.

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