Toxic algae is blooming more often in our lakes, reservoirs. Does that threaten our drinking water?
This article was produced as a project for the California Data Fellowship, a program of the Center for Health Journalism at the USC Annenberg School for Communication and Journalism.
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The night of Aug. 1, 2014, Toledo water officials received some troubling news.
For the first time in the city’s history, an unsafe amount of a dangerous algae toxin had been detected in its drinking water supply.
“We need to take action right now,” Public Utilities Director Ed Moore recalled saying when the city ordered customers not to drink, shower, brush their teeth or wash dishes with the tap water coming from their faucets.
The “do not drink” advisory lasted for three and a half days and forced more than 500,000 residents to rely on bottled water as officials tinkered with their water treatment process to ensure any toxins coming into the plant from algae-infested Lake Erie were destroyed.
Treatment Processes Are Usually Effective
Microcystin, the toxin that prompted Toledo to issue the health advisory, is produced by cyanobacteria, commonly called blue-green algae. The bacteria grow in lakes and rivers all over the world and its toxins are known to sicken people and animals.
In California, cyanotoxins have become more of a problem amid the drought and the same toxin that shut down Toledo’s water supply has been detected in lakes, reservoirs and streams across the state. But because standard treatment processes usually get rid of cyanotoxins, water officials say it’s unlikely a similar crisis would unfold here. Still, the risk exists.
“Based on the very limited data that we have so far we have seen that a lot of the typical treatment processes that are in use in California have been effective at removing toxins,” said Stefan Cajina, chief of the North Coastal Section of the State Water Resources Control Board’s drinking water division.
Cajina said there isn’t one disinfectant that works for everybody. Ozonation and granular or powder activated carbon are some of the most common strategies for dealing with cyanotoxins.
“It really depends on the individual circumstances,” he said.
Water Systems Should Monitor Toxins
The toxins aren’t currently regulated by the U.S. Environmental Protection Agency, so water districts in California are not required to test for cyanotoxins. Still, Cajina said it’s important for water system managers to assess whether their supplies are vulnerable to the toxins and develop a plan for how to deal with them.
“It’s a widespread issue,” Cajina said, adding that he was not sure how many of the roughly 7,500 public water systems in the state are at risk. “There are water systems all across the state of California that could be affected.”
The Metropolitan Water District of Southern California, which provides water to more than 20 public agencies serving millions of people in Los Angeles, Orange, Riverside, San Bernardino, San Diego and Ventura counties, is one of those water systems affected by cyanotoxins.
The district has detected microcystin in several of its reservoirs in recent years. It has also detected small amounts of the toxin in its treated water, but the toxin has never reached a level unsafe for human health.
“It doesn’t really concern us from that perspective, but it does require active management,” said Ric De Leon, former microbiology manager for MWD.
Risk is higher in recreational water
While there are documented cases of people getting sick and dogs dying after being exposed to cyanotoxins in recreational water, there are no documented illnesses linked to drinking water in the U.S.
That’s because the concentration of toxins in recreational water tends to be much higher.
“Drinking water is treated and delivered so there’s lots of opportunity to address anything that might be in the water,” said Susan Keydel, coordinator for the EPA’s California Watersheds Office.
Cyanotoxins cause a range of adverse health effects, including skin rashes, diarrhea, vomiting, confusion, liver damage and even cancer. But little is known about the health impacts from short-term exposure associated with recreational activities or chronic exposure associated with drinking water.
When it's not safe to drink water
Although the EPA does not currently regulate cyanotoxins in drinking water, it could in the future. The toxins have been listed on the agency’s contaminant candidate list since 1998.
Last year, the agency released 10-day health advisories for microcystin and cylindrospermopsin, another toxin produced by cyanobacteria. The advisories, which are only recommendations for water agencies, are an estimate of the concentration of the toxin that is not expected to cause any adverse health effects over a 10-day exposure period.
The advisories for microcystin are 0.3 micrograms per liter for infants and young children and 1.6 micrograms per liter for all other ages. The cylindrospermopsin advisories are 0.7 micrograms per liter for infants and young children and 3 micrograms per liter for all other ages.
If a water agency detects toxins above those levels the EPA recommendsthat it issue a “do not drink” advisory to the public.
In 2013, MWD detected 0.38 micrograms per liter of microcystin leaving the Mills Treatment Plant, which receives water from Silverwood Lake in San Bernardino County, but within three days the toxin was almost undetectable in the finished water, data from the district shows.
What went wrong in Toledo
When Toledo decided to issue the “do not drink” order almost two years ago, more than 1 microgram per liter of microcystin had been detected at the city’s water plant. At its peak, the city detected 2.5 micrograms per liter of microcystin in the finished water.
“It took us a couple days to bring those levels back down,” Moore said. The city lifted the advisory after the concentration of microcystin fell below 1 microgram per liter, a threshold determined by the World Health Organization in 1998.
The standards have since changed to a higher threshold for most people, so today the toxin concentration that prompted the advisory may not have triggered the same response.
“It was a learning experience,” Moore said, adding that he still thinks it was right to issue the advisory. “At the end of the day we’re protecting public safety and health and that’s our job, not to put people in harm’s way.”
Since then the city has quadrupled the amount of powder activated carbon and other disinfectants it uses to treat the water while it works toward designing a new plant with ozonation, which the EPA says is the “most efficient” way to destroy microcystin.
“Once we get that thing online we’ll all breathe a lot easier around here,” Moore said.
[This story was originally published by SGVT.]