Urban stormwater could release harmful chemicals to ground and surface water posing risk to human health, aquatic life

The researchers from the US Geological Survey and the US Environmental Protection Agency found 11 types of polluting and toxic substances in more than 90% of the samples


                            Urban stormwater could release harmful chemicals to ground and surface water posing risk to human health, aquatic life

Urban stormwater could be releasing harmful chemicals such as pesticides into groundwater as well as surface waters like rivers and lakes. These are the findings of a recent analysis of untreated urban stormwater from 50 rainstorms across the US.

The researchers from the US Geological Survey and the US Environmental Protection Agency (EPA) found 11 types of polluting and toxic substances - including the insect repellent DEET, nicotine, caffeine, and bisphenol A - in more than 90% of the samples.

“Eleven organic contaminants were pervasive across all samples (more than 90% detection): DEET (insect repellent, 98%), nicotine (alkaloid stimulant, 98%), caffeine (psychoactive stimulant, 96%), carbendazim (broad-spectrum fungicide and benomyl metabolite, 94%), methyl-1H-benzotriazole (corrosion inhibitor, 92%), p-cresol (wood preservative, 92%), cotinine (nicotine metabolite, 92%), desulfinyl fipronil (fipronil insecticide metabolite, 90%), bisphenol A (plastics, paper receipts, and epoxy resin production, 90%), fluoranthene (polycyclic aromatic hydrocarbon or PAH, 90%), and pyrene (PAH, 90%),” says the study published in American Chemical Society’s Environmental Science & Technology journal. 

The researchers state that some of the contaminants were present at levels known to be toxic to aquatic life, but those present at lower concentrations could also have effects when combined with all of the other substances in the water.

The researchers state that some of the contaminants were present at levels known to be toxic to aquatic life, but those present at lower concentrations could also have effects when combined with all of the other substances in the water. (Getty Images)

“Results indicate that urban stormwater is transporting an extensive mixture of organic contaminants with highly variable individual-component concentrations. The potential environmental effects from exposure to individual chemicals or chemical mixtures in stormwater samples are currently unknown or not well understood. The organic chemicals detected in stormwater cause concern for aquatic organisms because many of the chemicals persisting in the environment are known carcinogens (polycyclic aromatic hydrocarbons and polychlorinated biphenyls), bioactive (pesticides and pharmaceuticals), or hormonally active (biogenic hormones). The multiple detections per site, the individual concentrations, and sites with cumulative mixture concentrations exceeding 100,000 ng/L (nanogram/liter) are concerning as adverse environmental effects have been documented for some individual designed-bioactive contaminants even at low concentrations,” the researchers warn in their findings.

According to the US Environmental Protection Agency, stormwater pollution results from materials and chemicals that are washed into the storm drains from streets, gutters, neighborhoods, industrial sites, parking lots and construction sites.

This type of pollution is significant because, unlike the water that goes down a sink or toilet insides home, stormwater is untreated and flows directly to a lake, river, or the ocean.

Polluted run-off can contaminate not only water bodies, but also drinking water sources such as groundwater, and threaten seafood.

Previous studies of urban stormwater run-off have revealed a mixture of industrial chemicals, pesticides, pharmaceuticals, and other substances that, at certain levels, can be toxic to aquatic life. As a result, many cities and water-management agencies are trying to develop stormwater control measures to minimize the transport of these contaminants to other water bodies, such as rivers or aquifers. 

However, data from a wide variety of locations across the US are lacking.

At the national scale, little is known about the potential chemical exposures resulting from organic and inorganic contaminants in urban stormwater run-off or the possible effects on groundwater/surface water quality or ecosystem health.

To address this nationwide data gap, the US Geological Survey and US Environmental Protection Agency, in collaboration with municipalities, conducted a national-scale study of 438 organic and 62 inorganic chemicals in urban stormwater. The team cataloged and quantified the contaminants in urban stormwater from 50 storm events at 21 sites from 17 states across the nation.

The researchers analyzed a wide range of chemicals in urban stormwater collected during rainstorms.

They found a wide variety of contaminants that could potentially harm aquatic organisms in surface waters and infiltrate groundwater. The researchers also frequently detected prescription and non-prescription pharmaceuticals, indicating that the stormwater was contaminated with human waste, possibly from sewage leaks or other urban sources. 

Of the 438 organic chemicals examined, 215 (49%) were detected in one or more stormwater samples, while 223 (51%) not detected in any sample.

The number of organic chemicals detected in a single stormwater sample ranged from 18 to 103. Samples contained a median of 73 organic chemicals, with pesticides being the most frequently detected chemical group, accounting for 35% of total detections.

According to the research team, concentrations of the 215 detected organic chemicals spanned over six orders of magnitude from less than 1.0 to over 100,000 ng/L.

Of the 438 organic chemicals examined, 215 (49%) were detected in one or more stormwater samples, while 223 (51%) not detected in any sample. (Getty Images)

“Cumulative organic-chemical concentrations of samples ranged from 4,370 ng/L to 263,000 ng/L (median of 48,500 ng/L), with seven samples having a total concentration exceeding 100,000 ng/L. Of the 215 organics detected, 69 (32%) were frequently detected in more than 50% of samples. The 69 frequently detected organic chemicals accounted for 70% of the cumulative total 3,563 detections, and were composed of 21 pesticides, 16 PAHs, 11 industrial chemicals, 11 household chemicals, five non-prescription pharmaceuticals, three plant/animal sterols, and two prescription pharmaceuticals,” the findings state. 

According to the researchers, the findings highlight the need for more research about the long-term effects of these contaminants on aquatic organisms exposed to the stormwater.

“This study underscores the need for continued assessment of exposures and potential synergistic effects of contaminant mixtures in stormwater, potential contaminant source tracking, and mitigation methods,” says the research team.

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