A study recently published in the journal Environmental Science & Technology is the most recent, yet by no means the first analysis to show that U.S. septic systems are heavily contaminated with various potentially toxic chemicals. This is of particular interest because septic system discharges usually end up in local groundwater, and eventually make their way back into the population's drinking water.
CECs (contaminants of emerging concern) consist of chemicals discharged from household cleaning products, personal care items, hormones, natural household substances, flame retardants, hormones or various pharmaceuticals, which may have negative effects on human health. However, despite the risks associated with many of them, the Environmental Protection Agency does not have regulatory standards in place in what concerns the presence of CECs in drinking water.
The Silent Spring Institute, which conducted the research, synthesized "results from 20 studies of 45 OWCs [organic wastewater compounds] in conventional drainfield-based and alternative onsite wastewater treatment systems", and, for comparison, "31 studies of these same OWCs in activated sludge WWTPs" to study their capacity of removing these OWCs. Out of the 45 compounds of interest, some were effectively removed through the septic system processes; others, however, tended to remain in the water in significant quantities, including "TCEP, a carcinogenic flame retardant, an anti-epilepsy drug called carbamazepine, and the antibiotic sulfamethoxazole".
With approximately 20% U.S. households relying on septic systems (with much higher concentrations in certain areas), it is important that users are aware of these risks - and that they take steps to avoid them: using safer alternatives to potentially toxic products, properly maintaining septic tanks, and demanding EPA regulatory measures.