UNC study: Sludge-based fertilizer may be causing human illnesses
Treated municipal sewage sludge — the solids from sewage treatment — may be causing illness in people up to a mile from where it is spread on land.
Those are the findings from researchers at the Department of Epidemiology at the University of North Carolina’s Gillings School of Global Public Health.
The study, titled “Land Application of Treated Sewage Sludge: Community Health and Environmental Justice,” appears in the journal Environmental Health Perspectives. It involved residents from Virginia, North Carolina and South Carolina who live near fields where sludge is applied as a soil amendment. More than half of the people interviewed reported acute symptoms such as burning eyes, nausea, vomiting and diarrhea after sludge had been sprayed or spread. Neighbors of fields where industrial swine operations spray waste have reported similar symptoms.
“Study participants told us that the onset of the symptoms occurred while the sludge was being applied or soon after,” says Amy Lowman, MPH, research associate in epidemiology, and the study’s first author. “These were not one-time incidents, either. Respondents reported these illnesses occurring several times, and always after treated sludge was applied to the nearby farmland.”
Other symptoms reported by more than one respondent in the wake of sludge applications included difficulty breathing, sinus congestion or drainage, and skin infection and sores.
Respondents also reported sludge run-off into local waterways and cattle grazing on fields soon after sludge applications.
“Both of these situations are against state rules. If there is run-off of treated sludge there can be contamination of waterways or neighboring property,” Lowman says. “Livestock are not supposed to graze on sludge-applied fields for 30 days after application.”
In addition, all three states require signs warning that treated sewage sludge is in use on farmland, but several respondents reported that such signage was either not posted or not visible.
Study coauthor and principal investigator of the research, Dr. Steve Wing says, “Most people in towns and cities don’t know where their sewage sludge goes. If they had to live near where it is being spread out, they might be more concerned about this practice. Many respondents in our study said it’s not fair for rural people to bear the burden of urban waste disposal.”
Lowman does caution that the study’s findings are based on a relatively small sample size of 34 people and that better tracking of sludge applications and human health is needed to better document relationships between the sludge application and illness.
“However, we are talking about a material containing chemicals and organisms that can make people sick. Although the EPA promotes land application of sludge, it has not said it’s safe for people’s health or the environment,” she says. “More than half of the people interviewed reported similar symptoms. These reports came from individuals in three different states on separate occasions who live up to a mile from areas where sludge was applied. These findings are consistent with previous reports of health impacts and support calls for health and environmental agencies to pay more attention to the potential for sludge to impact people who live near land application sites.