Op/Ed: Biosolids Still an Unknown Quantity

In a recent letter to the editor, David Orvos, Sweet Briar College professor and biosolids monitor, defended the application of biosolids (sewage sludge) to farmland adjacent the Blue Ridge Railway Trail in northern Amherst County. Prof. Orvos implied but did not state that the expert panel convened by Gov. Timothy M. Kaine supported the safety of biosolid use on farmland. He also stated that “scientists are well aware of the components of treated secondary sludge.”

It is true that the Virginia expert panel (House of Delegates document No. 27, 2008) reported finding no scientific evidence of a causal link between biosolid application and human health outcomes but admitted that complaints exist and the science is insufficient.

The panel could find no evidence that biosolid contaminants could accumulate in plant crops or livestock but admitted that “whether there are longer term chronic effects from bioaccumulation of pharmaceutical and personal care products and other persistent organic compounds is more difficult to measure and has not been rigorously studied to date.”

Evidence of this possibility has since emerged. A Georgia farmer’s land was found to be poisoned by thalium and arsenic from sludge applications (Nature, May 2008, pages 262-3), and record levels of perfluorochemicals have been found in thousands of acres of Alabama farmland treated with sludge (Environmental Science and Technology, March 2009, pages 1245-6).

Further, the panel admitted that biosolids produce odor and that odors can potentially impact human health, well being and property values. They recognized that some surface water runoff and groundwater leaching is inevitable and, while nutrient management plans should control nitrogen and phosphorus run-off, little is known about the transport of other potential contaminants recently found to be ubiquitous in biosolid products.

Finally, they admitted that these same contaminants are linked with long-term negative health and reproductive impacts on fish and wildlife. The panel was charged with performing a detailed analysis of the composition of biosolids but declined because “the vast number of constituents in biosolids combined with the specialized analytical methodologies to detect and quantify these constituents involves significant cost.”

Five years earlier, the National Academy of Science, the most highly respected science body in the United States, reviewed the biosolids issue and concluded that while they could find no scientific evidence of a public health problem, the gaps in the science needed to be filled before the safety of biosolid application could be assumed. (See http://www.nap.edu/catalog/10426.html for free executive summary).

Specifically, they noted (1) a lack of exposure and health information on exposed populations, (2) a reliance on outdated risk-assessment methods, (3) a reliance on outdated characterization of the content of biosolids, (4) inadequate programs to ensure compliance and (5) a lack of Environmental Protection Agency resources devoted to the study of biosolids.

The fact that scientists do not know what’s in sludge is not surprising since the contents depend on what households and companies happen to flush down their toilets and pour down their drains, rather than on some well-defined production process. And each sample can contain a different mix of chemical compounds. An editorial in the internationally respected science journal Nature (March 2008, page 258) summarizes scientists’ doubts:

“It is possible that the millions of tons 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 program 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 of concern.”

In response to the National Academy’s demand for better science, the EPA just this year completed the Targeted National Sewage Biosolids Survey (EPA-822-R-08-014), testing for 145 contaminants in 74 randomly chosen wastewater treatment facilities in 35 states.

The following were found in at least 95 percent of samples: all 27 metals that were tested for, 12 pharmaceuticals, 9 steroids and all flame retardants. Each of four semivolatile organics and polycyclic aromatic hydrocarbons were found in at least 85 percent of samples. All of this is evidence of the persistence of organic wastewater contaminants — substances that are neither controlled nor tested for in the biosolids production process. These are compounds produced to improve industrial, medical and household products, including pharmaceuticals, flame retardants, plasticizers, pesticides and the like.

All are among the list of “Emerging Chemicals of Concern” that scientists have discovered have some new toxicity; are found to be building up in the environment, in humans, and in other living organisms; and have the potential to cause adverse effects on public health and the health of wildlife (California Department of Toxic Substances, 2007). They are “persistent” because most do not breakdown in the wastewater treatment process. Others are degraded into compounds made even more toxic by treatment and some persist in biosolids even after long periods of storage and are likely to accumulate in soils.

Literally, every analysis of sludge that has tested for these toxic chemicals has found them to be prevalent. Thousands of new chemicals are engineered each year, and many find their way into wastewater treatment products. Testing for and regulating this ever growing and ever changing list of potentially harmful substances in order to ensure biosolids safety would be a daunting task.

Prof. Orvos’ final claim is that biosolid application adjacent to a public recreation facility should have no consequences for its use.

According to current regulations, individuals residing near a biosolid application site must be notified. Required buffers around application sites may be extended if immune-suppressed individuals or individuals with respiratory problems reside close to the site (Virginia Department of Environmental Quality, 2008).

All of this implies, by extension, the moral and possibly legal obligation to notify trail users of potential hazards.

These are not imaginary risks. Recent research using DNA-based microbial source tracking has found particle contaminants from biosolid spreading (and tilling) to be transported at far greater distances and higher concentrations than previously believed (Atmospheric Environment, 2006, pages 7,034-7,045; Journal of Environmental Engineering, 2007, p 987-94).

Even if it were not for the health effects, noxious odors will discourage anyone considering trail use for several weeks following application, as complaint about odor emissions is one of the biggest problems land applicators face. Once the trail experience is tainted by odors and necessary health warnings, one would expect its use to decline, discouraging those very residents who have the most to gain from the recreational experience.

Bockstael is a professor emeritus at the University of Maryland, a past member of the Environmental Protection Agency’s Science Advisory Board, a fellow with the American Association of Agricultural Economists and a fellow with the Association of Environmental and Resource Economists. She lives in Amherst County and wrote this commentary for The News & Advance.