In the most recent peer reviewed scientific study (Organic Chemicals in Sewage Sludges 2006) from Cornell, Ellen
Harrison,, looked at organic chemicals which may be found in sludge.  This is the first scientific look at organics
since 1989 when
EPA acknowledged there were 14  of the chemicals in sludge which would cause cancer.
What Harrison found was that EPA still has no idea of just how deadly the chemicals in sludge will be to  homeowners,
farmers and their neighbors where sludge is disposed of as a fertilizer.

Harrison said:

Data were found for 516 organic compounds which were grouped into 15 classes. Concentrations were
compared to EPA risk-based soil screening limits (SSLs) where available. For 6 of the 15 classes of
chemicals identified, there were no SSLs. For the 79 reported chemicals which had SSLs, the maximum
reported concentration of 86% exceeded at least one SSL. Eighty-three percent of the 516 chemicals were
not on the EPA established list of priority pollutants and 80 percent were not on the EPA’s list of target
compounds. Thus analyses targeting these lists will detect only a small fraction of the organic chemicals in
sludges. Analysis of the reported data shows that more data has been collected for certain chemical classes such as
pesticides, PAHs and PCBs than for others that may pose greater risk such as nitrosamines