Bacteria may put sewage treatment workers at risk

Exposure to bacterial toxins may cause flu-like symptoms, breathing problems and skin reactions in some workers at sewage treatment plants, a study has found.

Researchers in the Netherlands found that workers at 67 sewage treatment plants had heightened risks of daily cough, shortness of breath, skin rash and flu-like symptoms such as headache and body aches and pains.

The culprit, say the researchers, seems to be the toxins that are released from both sewage bacteria and the bacteria that are used to remove pollutants from the wastewater.

Workers with higher exposure to the bacterial substances, called endotoxins, tended to have more symptoms, according to findings published in the American Journal of Industrial Medicine.

However, symptoms were not limited to maintenance workers and technicians; office staff, many of whom had cleaning tasks that could expose them to endotoxins, also reported breathing problems and other symptoms.

The findings indicate that workers at these plants should be better informed about the potential risks of exposure to biological agents, according to lead study author Lidwien A. M. Smit, a researcher at the Institute for Risk Assessment Sciences at Utrecht University.

Measures such as covering certain machines and other sources of endotoxin exposure could help, she told Reuters Health. There should also be mechanical ventilation in areas where airborne particles from sewage or sludge may be present, Smit added.

Though workers at the plants in this study wore masks during certain, specialized jobs, she noted, they did not do so for standard cleaning tasks around the plant.

The study included 468 employees at Dutch sewage treatment plants who completed questionnaires on whether and how often they suffered certain symptoms in the past year. At different points over one year, some of the workers wore portable air samplers that monitored their endotoxin exposure.

Smit and her colleagues found that workers had rates of daily cough, shortness of breath and asthma that were roughly 50 percent higher than those in the general Dutch population.

In addition, flu-like symptoms, breathing problems and skin irritation grew more common as workers' endotoxin exposure increased.

Respiratory and skin problems were also more common among employees who had worked at the plants for more than 20 years, suggesting that long-term exposure to bacterial toxins may be especially likely to trigger those symptoms.

SOURCE: American Journal of Industrial Medicine, July 2005.