Inflammatory Title, Insufficient Data Lead to Misinformation About Biosolids

A recent study published in the Journal of Environmental Health Perspectives by the School of Public Health at University of North Carolina (UNC) has caused quite a stir in the biosolids community. Entitled, “Land Application of Treated Sewage Sludge: Community Health and Environmental Justice,” the study[1] involved residents of North Carolina, South Carolina and Virginia who lived near fields where biosolids were applied. The UNC study focused on three areas: health impacts, environmental impacts, and social justice. On close analysis the study presented problems in the way that it was conducted, and in its misleading conclusions. But it was the press release entitled, “Study: Sludge-based fertilizer may be causing human illnesses,” which was picked up and sensationalized by the media[2] that has created the biggest backlash from biosolids advocates.


The inflammatory nature of the press release title is not supported quantitatively in the study. In fact, the study itself was a purely qualitative[3] and subjective exercise involving interviews with homeowners who live near farm fields where biosolids are applied. Those who had complained to local authorities about health problems resulting from the biosolids application were the first ones contacted by the researchers. There were only 34 study participants in all, most of whom were recruited through community-based groups, with only 5 random interviewees used as controls. The study described the interviewing process as using a “semi-structured open-ended discussion guide” – a nebulous description at best - and then summarized the findings by interpreting the personal statements of the interviewees. There was no fact-checking done on anything reported to the interviewers. They simply took the residents at their word when they “reported” illness and bad biosolids management practices to the researchers.


There were obvious and troubling issues regarding the findings reported for each of the areas in the study. As for health impacts, the residents claimed that their symptoms coincided with the application of biosolids but the researchers never interviewed the farmers to see what was being done to the fields on the days in question. Since some of the residents reported that no signs were posted about biosolids application, it’s very possible that some other product or chemical was being applied on the days in question. There was no quantitative epidemiological assessment correlating the symptoms to the biosolids’ application other than the residents’ say so.


Environmental impacts were also reported in the form of sludge run-off and letting cattle graze too soon after application of biosolids. Again, it seems that no attempt was made to contact the farmers about this, nor was there any mention of reports of violations of local, state or federal regulations for the farms in question. The researchers did not determine if the biosolids were Class A or Class B, or how or under what conditions they were applied, which could have had an affect on the odor or dispersal of particles.


On the issue of social justice, the researchers reported that “many respondents in our study said it’s not fair for rural people to bear the burden of urban waste disposal” but they never looked into the actual sources of the biosolids used on the farms nor did they take into consideration that it is the farmers who request biosolids from the municipalities! No one is “dumping” things near them out of social injustice.


The MidAtlantic Biosolids Association (MABA) has issued a rebuttal to this article and reported other inconsistencies. For example, they noted that the original study description submitted to the National Institute of Environmental Health Sciences (NIEHS) called for a longitudinal[4] study. Instead, the researchers only conducted single interviews.[5]


Reaction to the UNC report has been consistently critical. An article on the Virginia Biosolids Council website[6] entitled, “Study’s claims about biosolids fail scientific tests,” systematically debunks each negative claim. They questioned the credibility of the study by stating that, “The UNC study was not a scientific study to determine whether or not biosolids were linked to human illness. All the study did was collect the unverified claims, or ‘perceptions,’ of people who had been recruited for the study through ‘community-based groups’ that are opposed to biosolids.” The Council’s article also quoted from the report of a 2008 study by the Virginia Expert Panel on Biosolids[7] stating that “while the Panel, which included physicians and public health and environmental professionals, observed in its final report that while more research is always desirable, it ‘uncovered no evidence or literature verifying a causal link between biosolids and illness.’”

Now, although the scientific evidence in this study is non-existent, and the report heavily skewed to raise an alarm about the danger of biosolids application, the researchers’ interviews did result in one significant finding. This was buried under the innuendo of health risks, but it has validity. Most of those interviewed were upset at not being involved in the decision-making process or of being notified of the biosolids applications. Therefore, some of the reported adverse affects may have been aggravated by the perception of social inequality. This is an important aspect of biosolids management that cannot be underestimated. Communication, education, and transparency within the community by those involved with biosolids management can help defuse outrage and complaints and may help avoid the negative reporting and publicity that this type of study has engendered.



[1] Released on March 11, 2013 and authored by Steven Wing, Amy Lowman and others at UNC

[3] The two primary research methods are qualitative and quantitative. The purpose of qualitative research is to help understand and decipher social interactions. The primary purposes of quantitative research are to create and test hypotheses, look at cause and effect, and make scientific predictions. Qualitative research may focus on words, images or objects, while quantitative studies involve numbers and statistics.

In the conventional view, qualitative methods produce information only on the particular cases studied, and any more general conclusions are only propositions (informed assertions). Quantitative methods can then be used to seek empirical support for such research hypotheses. Source; Wikipedia

[4] A longitudinal study is a correlational research study that involves repeated observations of the same variables over long periods of time — often many decades.

[5] William Toffey’s rebuttal based on MABA’s report, “UNC Study Distorts Health Risks of Biosolids,”


[6] Virginia Biosolids Association;

[7] HJR694 Biosolids Expert Panel final report - December 22, 2008


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