Pepto_Miche11e_FlickrStormwater obviously causes problems for the environment and infrastructure, washing away salmon eggs in torrents of runoff and flooding basements. But does it threaten human health as well? You bet it does, and in ways that might surprise you.

Polluted runoff flushes raw sewage across beaches, triggers blooms of toxic algae in our drinking water systems, and contaminates shellfish and seafood we eat with bacteria and dangerous chemicals.

Over the past three years, sewage-tainted runoff has forced the closure of 32 Washington beaches, some for a couple of days, others for weeks. The problem is caused when rainwater mixes with the sewer system—sometimes by design and sometimes thanks to old sewer pipes that let the rain seep in. The cocktail of polluted runoff and raw sewage overwhelms the sewage treatment plant, forcing the combined sewer overflow (or CSO) to dump the waste into a nearby river, lake, or bay.

And what’s in that lovely concoction? Researchers find everything from salmonella bacteria to the parasite giardia, to Norwalk-like viruses. Ailments resulting from exposure to sewage-tinged water include:

diarrhea, vomiting, stomach cramps, fever, hepatitis, bronchitis, pneumonia, and swimmers itch.

People get sick by swallowing the water either when recreating in or when their drinking water becomes contaminated. You can get sick simply by inhaling small droplets, or through contact with skin, eyes, ears, and cuts. Children, pregnant women, the elderly, and any immuno-compromised people are most at risk. (This 2004 EPA report to the Congress gives a great overview of CSO health impacts.)

Grossed out yet? Let’s delve deeper.

  • The National Research Defense Council and Environmental Integrity Project released the report “Swimming in Sewage” in 2004, which also documented the effects of sewage pollution, though the focus was broader than the EPA’s combined sewer overflow study. The nonprofit groups’ report included this now oft-cited bit of data specific to overflows: 

    Each year, 1.8 million to 3.5 million illnesses are caused by swimming in water contaminated by sewage overflows, and an additional 500,000 from drinking contaminated water.

    Glass half empty

    One of the most troubling effects of polluted runoff is the contamination of peoples’ drinking water—something we might take for granted as safe. More than half of the documented waterborne disease outbreaks in the US since 1948 occurred after extreme rainfalls, according to a 2001 peer-reviewed study. A 2003 study likewise made the connection between polluted stormwater runoff and waterborne disease.

    Northwesterners generally can expect clean, safe drinking water to flow from their taps. But that’s not always the case. There are numerous local examples of drinking water that’s fouled when sewage and stormwater flow into waterways, or when storm runoff directly dumps fertilizers, fecal bacteria, and other pollution into our drinking water sources.

    In one of the larger outbreaks of illness caused by contaminated drinking water, some 3,000 people in Oregon got sick in the early 1990s from water that came from a river that was tainted by sewer waste (EPA, table I.1).

    Lake Whatcom, the sole source of drinking water for the city of Bellingham is under increasing threat from polluted runoff as developments continue to sprout up around the water body. The lake is most at risk from too much phosphorus, which comes mostly from fertilizers, and from fecal coliform flowing into the lake from tributary streams and rivers.

    The phosphorus is a problem in part because it stokes the growth of plants and algae in the lake, and that added plant matter “can require an increase in drinking water treatment chemicals that form carcinogenic byproducts and add treatment costs,” according to a 2008 study by the Washington state Department of Ecology.

    And just this month, some of the residents of BC’s Salt Spring Island were told not to drink their tap water because of toxic contamination from algae. Where did the nasty plants come from? The algal bloom was triggered as “a result of excess phosphorous running into the lake from surrounding properties,” according to the Gulf Islands Driftwood. When the algae die, they decompose and release a toxic compound that can’t be eliminated by boiling the water. The ban could be in place for weeks.

    Something fishy

    While it can be relatively straightforward to make the link between stormwater runoff and drinking water pollution and illness from recreational exposure, it’s a little more challenging to make the direct connection to seafood contamination. But there are incidents of illness and pathways of exposure that make clear some effect is likely.

    In the late ’80s, at least 61 people around the US contracted Hepatitis A after eating oysters contaminated by human fecal waste (EPA, table I.3).

    In an analysis of the 95 spots around Puget Sound where oysters, clams, and other shellfish are commercially harvested, more than one-third of the locations had elevated levels of fecal waste in 2007. The entire stretch of shoreline from north of Everett to south of Tacoma is unsafe for the recreational harvest of shellfish from the beaches. Some of the contamination likely comes from leaking septic systems or sewage plants, but polluted stormwater runoff certainly contributes some of the bacterial waste.

    And there are the toxic chemicals that are spewed into waterways with stormwater. They include oil and grease, heavy metals, flame retardants, PCBs, polycyclic aromatic hydrocarbons (PAHs), and other pollutants. Washington’s Department of Ecology estimated that at least 14 million pounds of pollutants were dumped by stormwater into Puget Sound alone each year (the agency will release updated pollution estimates in March—stay tuned!).

    PAHs in seafood got a closer look recently thanks to the massive BP oil spill in the Gulf of Mexico. The compounds, which are found in petroleum products and are formed when fossil fuels are burned, accumulate in organisms. Larger PAHs can cause cancer in humans, while smaller PAHs can be toxic to marine life. According to Ecology, at least 350,000 pounds of cancerous PAHs are spilled into Puget Sound each year with our polluted stormwater, while 760,000 pounds of the smaller PAHs make their way across the landscape and into the Sound.

    There are health consumption advisories for a variety of Northwest seafood due to toxic conta
    mination, again, som
    e of which is coming from polluted stormwater. People are advised to limit their consumption of Puget Sound rockfish (mercury), English sole (PCBs, mercury), and chinook salmon (PCBs). In Oregon, there are warnings against eating a range of fish from the Columbia River, the Willamette River, Portland Harbor and other lakes, reservoirs, and rivers due to mercury and PCB pollution. 

    Where do we go from here?

    Addressing stormwater and CSO pollution is challenging because it comes from everywhere. That’s why a coalition of citizen groups, local governments, and labor leaders is backing legislation being considered in Olympia right now to charge polluters to help cleanup stormwater. Additionally, lawmakers in Oly and Salem are considering bans on some of the pollutants themselves including coal-tar asphalt sealants (HB 1721) and copper-containing brake pads for vehicles (SB 945).

    There are smart, affordable, long-term solutions to reducing and cleaning up our polluted runoff, namely low-impact development. But it’s going to take a serious commitment and significant investment in that kind of community-wide and regional planning to get us there.

    An Ecology report on the Lake Whatcom drinking water situation had this advice, which was basically a call to low-impact development (emphasis mine):

    It will be up to local government leaders to develop strategies and pass laws that improve stormwater management so stormwater is absorbed, filtered, and released into the lake more naturally, as if most of the development is not there.

    Pepto photo from Flickr user Miche11e used under the Creative Commons license.