Pharmaceuticals and Personal Care Products in US Biosolids

Since the 1988 U.S. ban on ocean dumping of sewage sludge, the majority of these materials are disposed of on land as biosolids. To provide fundamental data for risk assessment concerning the environment, crop plants, and humans, several studies have been conducted that aimed at quantifying the load of pharmaceuticals and personal care products (PPCPs) as well as other emerging pollutants of concern in biosolids. So far, two large studies exist that analyzed biosolids samples representing the whole U.S. Both sample sets were collected by the U.S. Environmental Protection Agency (EPA) and analyzed by the same contract laboratory that developed the EPA method 1694 for analysis of PPCPs in biosolids and other matrices. The samples were analyzed using liquid chromatography tandem mass spectrometry and quantified using isotope dilution as well as conventional use of internal and external standards. The present meta analysis scrutinizes the findings and approaches of the two studies and puts them in context to potential environmental risks that should be considered. Both the EPA's Targeted National Sewage Sludge Survey (TNSSS) and the analysis of a comparable sample set collected in 2001 revealed concentrations of several antimicrobials and antibiotics in the mg kg(-1) dry weight range. Prevalent contaminants were triclocarban, triclosan, ciprofloxacin and ofloxacin, followed by a number of tetracycline antibiotics. A comparison of the two datasets and study designs showed that combining a large number of individual samples to mega-composite samples is a suitable approach for identifying prevalent contaminants and for obtaining representative mean concentrations. Whereas the use of mega composite samples can result in significant time and cost savings, this study design strategy tends to yield lower numbers of total analytes detected, lower detection frequencies for individual analytes and it limits the detection of spatial (geographical) patterns in analyte occurrence. The findings of both nationwide studies provide a critical data basis for future risk assessment concerning the safety of biosolids application on agricultural and recreational land. Risks of primary concern identified in this work are the promotion of antibiotic resistance in the environment, adverse effects on soil microbial communities and plants, as well as the possibility of direct exposure of consumers to antibiotic residues contained in food crops grown on biosolids amended fields.