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People have used human waste for thousands of years to fertilize cropland and gardens. In comparison, federal regulations for using such “biosolids” on land are young: They have been in effect for about 30 years. Nonetheless, they are out of date and may put public safety at risk, according to researchers. Their study finds that biosolids that meet federal standards may still spread emerging pathogens such as noroviruses, a family of microbes that causes stomach flu (Environ. Sci. Technol., DOI: 10.1021/es200566f).

Waste processors have several options for treating biosolids to remove pathogens or reduce their levels, including heat treatment, composting, and irradiation. In 1993, the Environmental Protection Agency updated its regulations by establishing standards for pathogen levels in biosolids destined for land applications, including fertilizing crops. One goal of these regulations was to lower the risk of infection for people living or working in areas near treated lands. In those areas, people may breathe in Salmonella, enteroviruses, and other pathogens contained in the dust blown off biosolid-treated lands.

The regulations have worked well on Salmonella and enteroviruses, says Jordan Peccia, an associate professor of chemical and environmental engineering at Yale University. To find out whether they also protect against emerging pathogens, he and his colleagues compiled data from previous studies that had measured the pathogen content in biosolids deemed safe for land application, and did new risk analyses.