WARNING!
This is an older article that may not reflect Dr. Mercola’s current view on this topic. Use our search engine to find Dr. Mercola’s latest position on any health topic.
It could soon be declared unsafe to swim in lakes, due to the presence of microcystins and other toxins that can be found in algae blooms. Microsystins are nerve toxins produced by freshwater cyanobacteria (blue-green algae) that can cause fever, headaches, vomiting and seizures.
Cyanobacteria and their toxins (which include microsystins and others) can also damage the liver and cause kidney, cardiac, reproductive and gastrointestinal effects.1
The toxic algae are showing up in lakes across the U.S., threatening not only swimmers but also wildlife and those who use the lakes for drinking water. The Environmental Working Group (EWG) created an interactive map showing the location of algae blooms reported from 2010 to the present, and they’ve increased alarmingly.
While there were about 60 news reports of algae blooms in 2010, this jumped to about 440 in 2018.2 “We have been startled to find that these outbreaks are erupting everywhere: from the East Coast to the West Coast, from the Great Lakes to the Gulf of Mexico,” EWG reported.3
Toxic algae detected in 48 US states
The EPA’s National Lakes Assessment has detected microcystin in freshwater in all 48 contiguous U.S. states.4 The EPA also found that cyanobacteria are on the rise. In 2012, microcystin was detected in 39% of lakes. In comparison to 2007, conditions worsened in 2012, with cyanobacteria detected in 8.3% more lakes. There was also a worsening in microcystin, with a 9.5% increase in the toxin from 2007 to 2012.5
While the report noted that microcystin levels rarely reached moderate or high levels of concern, it’s possible that additional testing later in the season may have yielded higher concentrations. According to EWG:6
“Notably, more than 90 percent of the samples were taken only once during the assessment, and nearly a quarter of the samples were collected during May and June, when conditions are not as conducive to algae growth.
The EPA data show higher monthly averages for microcystin samples collected in the late summer and early fall. In 2007, monthly averages of microcystin in August and September were five times higher than in May, June and July. In 2012, monthly averages were three times higher for August and September compared to the earlier months.”
Many states aren’t monitoring blue-green algae
EWG cited a “lack of standardized data among states [that] makes systematic data collection and analysis extremely cumbersome.”7 In a survey of microcystin data from U.S. states, EWG reported that only 20 had results available online or upon request.
Further, while 30 states post advisories for public beaches to warn of toxic algae, or maintain maps of areas where toxic algae blooms have occurred, 20 states post only basic information, without advisories.8 What EWG did analyze, using microcystin data from lakes in 14 states and Lake Erie, revealed cause for concern. EWG explained:9
“Eight of the 14 states — Iowa, Washington, Nebraska, Kansas, New York, Illinois, Florida and Ohio — tested regularly and accounted for 97 percent of the results. The remaining states tested only a few times a year or during an active advisory.
Of the more than 10,400 samples collected by states, EWG found almost 9 percent, or over 900, exceeded the EPA’s 2016 4 µg/L draft advisory level. In eight states — Iowa, Illinois, Kansas, Oregon, Florida, New York, Wyoming and California — samples exceeded the World Health Organization’s 1 µg/L drinking water advisory more than 20 percent of the time.”
Further, while the EPA’s 2016 draft assessment recommended recreational or swimming advisories be issued if microcystin levels reached 4 µg/L, the advisory was revised in May 2019 to 8 µg/L10 — a level that’s higher than public action levels set by several states to protect public health. According to EWG:11
“In 2016 the EPA drafted a study on “Human Health Recreational Ambient Water Quality Criteria or Swimming Advisories for Microcystins and Cylindrospermopsin” to establish advisory guidelines for recreating in water with the presence of microcystin.
The study notes that some state health and environmental agencies, including those of Indiana, Ohio, Washington, Vermont and Virginia, recognize 6 µg/L6 as a public action level for recreational waters and that a handful of states have beach and lake test programs.”
What happens when toxic algae invade drinking water?
Surface water, which includes water in rivers, lakes, streams and reservoirs, is a major source of drinking water in the U.S.12 — one that can become contaminated by toxic algae. In 2014, citizens in Toledo, Ohio, were warned not to drink their tap water as it was found to contain significantly elevated levels of microcystins, caused by algae blooms in Lake Erie.13
It was the first time microcystin was implicated in contaminated drinking water, but it wasn’t the last. In Salem, Oregon, algae blooms in Detroit Lake triggered a drinking water advisory in 2018.14 In Rushville, New York, residents were also warned not to drink or cook with tap water due to blue-green algae blooms found in Canandaigua Lake.15
Pet owners also need to be on the lookout for toxic algae, as dog deaths have been reported in Texas, Georgia and North Carolina in 2019, after dogs came in contact with the algae.16
In Austin, Texas, an alert was issued warning people to “keep pets away from Lady Bird Lake” after toxins were detected in algae near Red Bud Isle. People were also warned to “minimize their exposure to the water and avoid all contact with algae.”17
Outside the U.S., meanwhile, algal blooms spanning thousands of miles have been recorded in China and Australia, while microcystin has been detected in more than 240 bodies of water in Canada. In Greece, Italy and Spain, algal blooms are also a problem and reported to cost the economy $355 million annually.18
Toxic algae cause both short and long term health risks
In the short term, exposure to toxic algae can cause acute symptoms like abdominal pain, diarrhea, neurological symptoms, irritation to your skin, eyes, nose and throat, vomiting and headache.19 In the long term, toxic algae may cause liver and kidney damage, as well as promote the growth of tumors20 and induce neuroinflammatory effects.21
You can be exposed to blue-green algae by swimming or wading in contaminated water (even if you don’t see a bloom), eating contaminated seafood, drinking contaminated water or even by breathing in contaminated mist from the water, such as may occur during recreational activities.
It’s also been suggested that toxic biological material from algae blooms may aerosolize into the air when waves break against the shore,22 representing another potential route of exposure. Study author Andrew Ault from the University of Michigan said in a news release:23
"Harmful algal blooms have been expanding as an important issue we're dealing with, particularly for the Great Lakes.
We've realized that not only are these important for water quality issues, but that you also generate atmospheric pollutants from these harmful algal blooms. We're the first to show that wave-breaking of these blooms can release material into the atmosphere, which can have impacts on people breathing it in."
What’s causing the rise in toxic algae
Algae are common to fresh and saltwater environments and provide food and oxygen to marine life, such as fish, as long as they’re in proper balance with the ecosystem around them. However, when provided with an excess of nutrients, such as occurs when fertilizer runoff from farms contaminates waterways, algae can quickly grow out of control.
According to the EPA, harmful algal blooms require sunlight, slow-moving water and nutrients (i.e., fertilizers such as nitrogen and phosphorus) to occur. “Nutrient pollution from human activities makes the problem worse, leading to more severe blooms that occur more often,” they state.24
These human activities include industrial agriculture and concentrated animal feeding operations (CAFOs). For instance, fertilizer runoff was blamed for toxic algae taking over Florida coastlines in 2016. It got so bad in some areas that the blue-green algae could be seen from space.25
The algae bloom started in May 2016 in Florida’s largest freshwater lake, Lake Okeechobee, which serves as a catchall for runoff from surrounding farms and neighborhoods.
In a report released by environmental group Mighty Earth, massive manure and fertilizer pollution churned out by meat giant Tyson Foods is also blamed for the largest dead zone, caused by toxic algae blooms, on record in the Gulf of Mexico.26
How to spot toxic blue-green algae
The name blue-green algae is somewhat misleading, as toxic algae can be green, blue red or brown. Further, some green algae are harmless. The fact is, you can’t determine if algae floating on a water surface is toxic just by looking at it, but if you see dead fish in the water, it’s a red flag that the algae could be dangerous.
The Illinois Environmental Protection Agency and Department of Public Health also recommend avoiding contact with water that:27
- Looks like spilled, green or blue-green paint
- Has surface scums, mats or films
- Is discolored or has green-colored streaks
- Has greenish globs suspended in the water below the surface
In addition to avoiding contact with lakes, rivers and other surface waters that could be contaminated (and keeping your pets out of the water as well), you can help protect yourself by installing a water filter on your tap to help reduce or remove cyanobacteria.
On a larger scale, stopping the source of pollution by cutting excess runoff of fertilizer will be necessary. Better land-use management that addresses fertilizer runoff, along with dramatic reductions in synthetic fertilizer use, would be a good start. You can help on an individual level by choosing organic or biodynamically grown foods instead of those produced on CAFOs.
As for whether or not to swim in a lake or river that has green algae, it’s best to avoid it. Even if the local health department hasn’t issued any advisories, it’s not a guarantee of safety, as not all waterways are tested. If you think you’ve come into contact with toxic algae, rinse off your skin and seek medical attention.