Nature 453, 258 (15 May 2008)
Some 30 years ago, as the United States began to tighten its environmental regulations on residential and industrial wastewater, operators of sewage-treatment plants embraced what seemed an eminently sensible idea. They decided to take the rich organic sludge left over after clean water is extracted and sell it to farmers as fertilizer. The practice proved popular, and has become increasingly common internationally. Today, some 60% of sludges, innocuously dubbed ‘biosolids’ by the US Environmental Protection Agency (EPA), are used as fertilizer in the United States.
The programme might well be as sensible as it seems. It is possible that the millions of tonnes of sludge being spread across the rural landscape contain no significant levels of toxic chemicals, heavy metals or disease-causing organisms. It may all be perfectly benign. The disturbing fact is that no one knows.
In what can only be called an institutional failure spanning more than three decades – and presidential administrations of both parties – there has been no systematic monitoring programme to test what is in the sludge. Nor has there been much analysis of the potential health effects among local residents – even though anecdotal evidence suggests ample cause for concern.
In fact, one of the studies used to refute potential dangers, published in the Journal of Environmental Quality in 2003 by researchers at the University of Georgia in Athens, has been called into question (see page 262). Even the National Academy of Sciences seems to have been taken in. A 2002 report from the academy cited the then unpublished Georgia work as evidence that the EPA had investigated and dismissed claims that sewage sludge had killed cattle, but the study had not looked at the dairy farms in question. And although it may be technically true that there was no documented evidence of sludge applications causing human illness or death, the academy also cited work by an EPA whistleblower, David Lewis, suggesting at least an association between these factors. If anything, recent research underscores those findings.
The Georgia citation notwithstanding, the academy did outline a sound plan for moving forward. It recommended among other things that the EPA improve its risk-analysis techniques; survey the sludges for potential contaminants; begin tracking health complaints; and conduct some epidemiological analyses to determine whether these reports merit concern.
The EPA has completed none of those tasks. Six years later, the agency is only now trying to finish its evaluation of potential contaminants and has yet to establish a system for monitoring reports of health problems. Agency officials say that they are working on risk-analysis tools, but have yet to undertake any kind of epidemiological studies. The EPA certainly has other competing priorities, and the fault here does not lie only with the current administration or any single researcher. Regardless, these safety questions deserve answers, and the EPA should be able to deliver them. It is time to get the data.