Perrin Ireland is senior science communications specialist for the Natural Resources Defense Council. This post was adapted from one that originally appeared on the NRDC blog Switchboard. Ireland contributed this article to LiveScience's Expert Voices: Op-Ed & Insights.
This weekend is the last beach hurrah for many of us as we prepare for fall — but know before you go to the beach this weekend that it will be safe for you and your family to swim.
I recently had conversations with two experts who revealed to me the science behind understanding and preventing beach water contamination. Earlier this summer, I had a Skype chat with Rachel Noble, who I had heard speaking on NPR's Science Friday about contaminated beach water when NRDC's 23rdTesting the Waters report first launched in June. In July, I spoke with Steve Fleischli, senior attorney and director of the water program at NRDC, on his thoughts about "urban slobber," EPA standards for what defines safe swimming water, and how people individually can prevent runoff.
The following three videos and highlights are the product of those frightening, enlightening conversations.
Rachel Noble's research on bacteria
While talking to Rachel Noble, I learned several points about the nature of microscopic bacteria and why poopy water makes us sick.
First, whether something can make more of itself on its own, or replicate is a big piece of how we determine whether it's living or not. Viruses are technically not living, because they depend on their host to replicate. Creepy. A microbe is, roughly speaking, an organism that's microscopic. We use microbe to describe viruses, bacteria and protozoa.
Second, bacteria are dose dependent — you have to get a high enough threshold of them in your body to get sick, and the amount you get determines how sick you get. Viruses are not dose dependent — just one can make you sick as a dog.
Feces are power-packed with bacteria and viruses. There can be millions or billions of viruses in one gram of feces or one milliliter of feces-contaminated water. Some think that, "dilution is the solution," but when you have a stormwater pipe or sewage break running water into the beach,that's a contaminant-loaded quantity of water, and it's not diluted enough at all.
Luckily, most of the sewage across the country is treated. (Phew.) Chlorine kills off a lot of bacteria — like adding bleach to a toilet at home (which is not so environmentally friendly, but certainly helps kill things.) But stormwater, which is not treated, delivers a healthy dose of feces-contaminated water to beaches.
Local economies suffer because of beach water contamination:
According to Noble, in North Carolina, a lot of people make their living harvesting oysters and clams. Given the way land use has changed — and how impervious surfaces have increased, allowing more stormwater runoff to pollute harvesting waters — families that have been harvesting shellfish for generations are increasingly unable to make a living this way. Oysters are filter feeders — they filter water through their bodies and concentrate the bacteria through their guts — and, as Dr Noble pointed out, the guts are what we eat! Eating raw oysters is particularly dangerous if the water is contaminated. When there's a storm and harvesting waters are closed, that's several days of harvest lost — no income for oyster farmers for as long as it takes the water quality to improve.
Beaches and beach industries also lose out from closures because of polluted beach water. NRDC reports in this year's Testing the Waters that it's estimated in some locations a typical swimming day at the beach is worth $35 per beach visitor, which no one gets to earn when the beach is closed. According to the report, "One study estimated economic losses as a result of closing a Lake Michigan beach due to pollution could be as high as $37,030 per day."
There are also public-health costs. The NRDC report references a Southern California study which found that fecal contamination at Los Angeles and Orange County beaches caused up to 1.5 million excess gastrointestinal (GI) illnesses (although I can't imagine a GI disease that's not excessive), with a public health cost each year of $21 million to $51 million.That's a ton of money going towards sicknesses we could avoid with better water quality testing and reporting.
How to know before you go
To protect yourself from contaminated beach water, swim at beaches that test water frequently. Dr Noble's lab has been advancing water-quality testing techniques, creating a test that takes only three hours to produce results. The old way to test beach water quality, which is still employed at a lot of beaches, involves collecting water, filtering it and putting it on a petri dish that has food for the bacteria. Then it is incubated it for 24 hours, and when a technician analyzes it, little dots appearing on the petri dish reveal how much bacteria is living in a given quality of that beach water.
The rapid test Noble's lab is developing involves the same collecting and filtering, but then she blends up the cells collected in the water. She runs this cellular mush in a machine that tests the level of DNA in that sample (quantitative polymerase chain reaction (PCR), if you must know) and it takes two to three hours to get results back on how much bacteria is in the water. Steve Fleischli encourages the use of these methods, because as he says, you could go out early in the morning on a Saturday morning and have results by mid-morning for whether it's safe for folks to swim.
Anyone can help reduce runoff, but it's the U.S. Environmental Protection Agency (EPA)'s responsibility to warn the public about a threat in the first place. Both Noble and Fleischli hope that use of rapid methods will increase, and that EPA will push the use of the best technology and science available to protect human health. There's good science that EPA has conducted, Noble says, that shows quantitative PCR is more predictive of illness. Now it's time for EPA to give some incentive for people to use those technologies at the beaches with the highest numbers of people. The agency has the chance to make national beach water standards far more protective of our health. EPA should revisit its new standards to ensure they are more protective of public health, and EPA should maintain funding for beach monitoring and notification programs.
Heed the signs, and go to beaches that postnotices promptly when there's a problem. Fleischlimentioned that he's been concerned to see people swimming directly in front of signs warning of contamination at the beach. That would make sense, actually, in light of what Noble shared on this issue: Sometimes the signs warning swimmers that water is contaminated are placed directly on top of pipes, and she's found in asking beachgoers that many don't know the sign means there's "a source of contamination that's diffusing in every direction."
Avoid the flow. Stay clear of flowing storm drains on the beach — the farther away you are, the better. Those drains are often a source of contamination and typically convey polluted runoff from nearby (or even far-away) streets and neighborhoods. Those drains can also contain raw or partially treated sewage. Noble's lab has been researching safe swimming distances from stormwater pipes. The official verdict is still out, but the bottom line is that for small storms, contamination from a pipe spreads 200 to 400 meters up and down a beach from the pipe. That's 800 meters total, with just one sign to mark it right at the pipe — this is a big deal, Noble says.
A good rule of thumb is to avoid swimming at the beach for at least 24 hours after it rains and 72 hours after heavy rains. Nobel wants to find out how long bacteria infest waters after a storm, and how far they roam. She's on a mission to figure out how to position signs to capture the most accurate diffusion of contaminated water, to more effectively warn the public.
Am I any safer swimming in a public pool?
When I asked this question, Dr Noble reminded me that she's not a risk-assessment scientist — a good point. Once I clarified my question was about viral infection, not head-hitting, she gave me a frightening analogy: "If you're going to a public pool that has a hundred kids in it, and thirty of those kids have diapers on, and you're talking about going to a beach with no storm pipe, I'd rather go to the beach." She referenced Sam Dorevitch's comments on Science Friday about risk, and how it's most important to be educated about what can comprise a risk. Chlorine won't kill everything — if there are ten kids with diapers, and two might have "loaded" diapers, it's important to consider that there is less water to dilute things in a swimming pool — it's a bit of a poop risk.
Ireland's most recent Op-Ed was Megalodon Myths Dispelled: Sharks Deserve Better than 'Shark Week'. The views expressed are those of the author and do not necessarily reflect the views of the publisher. This article was originally published on LiveScience.
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