Researchers identify potential dangers of biosolid fertilizers

Fertilizers made from waste sludge from wastewater treatment processes may contain traces of potentially harmful organic chemicals, according to a new study by researchers at Johns Hopkins University.

The research, published in Environmental science and technology, provides one of the most comprehensive reviews of the chemical composition of so-called biosolids across the country and is the first step toward identifying common chemical contaminants that may require government regulation. The findings could help the U.S. Environmental Protection Agency prioritize which organic compounds to investigate further, the researchers said.

“We've been relatively unclear about possible organic risks in biosolids, and we need to know if there's compelling evidence that we don't know about,” said Carsten Prasse, an assistant professor in the Department of Biosolids. 'environment. Health and engineering that studies environmental contaminants. “Regulators need to know what these types of fertilizers are made of to determine how they can be used responsibly.”

Using analytical chemistry techniques capable of identifying thousands of chemicals, Prasse and his team analyzed 16 biosolids samples from wastewater treatment facilities in nine U.S. and three Canadian cities. The samples contained traces of pharmaceuticals, industrial chemicals and various perfumes. Among them were bisphenol A (BPA), commonly found in plastics, and carbamazepine, a drug used to treat epilepsy and bipolar disorder.

“Since there are so many compounds in biosolids, the question we asked was how do we sort? How do we find the prevalent and potentially problematic chemicals, which EPA and other scientists should investigate before proposing regulations.” said Prasse.

The researchers then created lists of chemicals found in each sample and compared them to compounds that appeared in multiple locations across the country. They identified 92 compounds present in 80% or more of the samples.

The researchers then compared these 92 compounds with the EPA's CompTox Chemical Dashboard, a database that details the properties, hazards and potential risks of thousands of chemicals. The dashboard helped the team identify chemicals most likely to pose a threat to human health or the environment.

“We're not saying these compounds pose a risk at this time because we haven't done a formal risk assessment,” said Matthew Newmeyer, a research associate at the Bloomberg School of Public Health and first author of the study. article. “We are saying that these can potentially be problematic and that we need more information in order to ensure the safety of these biosolids.”

Using biosolids can be beneficial, researchers say. They are rich in nitrogen, phosphorus and other nutrients that promote plant growth. They require less energy to manufacture than synthetic alternatives. And wastewater treatment facilities can sell biosolids to generate revenue to offset treatment costs and reduce waste sent to landfills or incinerators.

According to the EPA, more than half of the 3.76 million tons of biosolids produced in the United States in 2022 fertilized farmland, golf courses and other landscaped areas. Although direct contact with biosolids is likely limited to occupational exposures, the population at large could be exposed to contaminants absorbed from crops grown with such fertilizers, the researchers said.

The team plans to measure compounds identified in biosolids and vegetables grown in biosolids-amended soil to determine if their concentration levels warrant concern. Researchers are also studying the risks for farmers, landscapers and composters who work with biosolids.