SALT LAKE CITY — Roughly 330 people were exposed to toxins caused by a large algal bloom that erupted at Utah Lake and spread to the Jordan River system, prompting advisories to stay out of the water and causing concerns over farmers' crops.

Officials also report that another 20 exposures involve animals, mostly dogs that have entered contaminated water.

Riverton, South Jordan, West Jordan and Herriman shut down secondary water systems, and the Welby Jacob Canal Co. also cut off users for fear that harmful levels of cyanobacteria could contaminate crops.

The state Department of Environmental Quality reports 100 dead ducks were found in one of the more than half-dozen canals that comes off the Jordan River, and tests are underway to determine if the bloom's toxins are responsible.

Barbara Insley Crouch, executive director of the Utah Poison Control Center, said about 330 cases have been logged of exposure to cyanobacteria from the algal bloom, with symptoms that include vomiting, headache, diarrhea and abdominal pain. At high thresholds, the toxins can cause respiratory problems and skin irritation.

"These were individuals who were recreating on or near the water at Utah Lake" and may have also been exposed at the Jordan River, the lower Little Cottonwood Creek or the lower Spanish Fork River, Crouch said.

Utah Lake remains closed and people should stay out of the Jordan River along its 51-mile corridor through Salt Lake County, officials said.

A team of divers cut off intake access from the Jordan River on Monday morning for a secondary system that serves the Rose Park Golf Course, and Kennecott Land shut down access to Oquirrh Lake at Daybreak and Brookside Stream.

Salt Lake City was also coordinating with police officers to urge homeless people who camp along the river to stay clear of the water.

"There is not a lot of human health information known about this," Crouch noted, stressing that people aren't generally "gulping" great amounts of the contaminated water. However, the risk is high with animals, particularly dogs, that may be fetching balls or other toys and drinking as they swim. She said there were about 20 cases of animals coming in contact with contaminated water.

Dr. Chris Crnich, field veterinarian for the Utah Department of Agriculture and Food, said exposed animals will experience lethargy, vomiting and diarrhea. At high exposure, death can occur. Two years ago, a family's dog died after playing in the water at Utah Lake at the Lindon Marina.

Farmers and others who rely on Utah Lake have been advised to refrain from using the water on vegetation, with Crnich noting that danger exists from pressurized systems that may cause the bacteria to become aerosolized. That warning has been expanded to include Jordan River water users.

"We don't know how toxic it is," Crnich said. "We are going to stick to our guns and play it safe and ask people to not use it for irrigation purposes."

Walt Baker, director of the Utah Department of Environmental Quality's water quality division, said people can start experiencing physiological effects of exposure with levels as low of 20,000 cells of cyanobacteria per milliliter.

Samples taken Friday at Utah Lake's Lincoln Beach showed 2 million cells per milliliter; 762,263 cells per milliliter at the North Branch canal were measured Saturday; and tests showed 380,112 cells per milliliter at Jordan River at 4500 South.

Further testing will show how much cyanobacteria exists in the impaired water, as well as the degree of the contamination's toxicity.

The Utah Farm Bureau has been working with state agricultural officials and Utah State University's Extension Service to assess threats of contamination to produce, but the lack of information on the science has been frustrating.

"Right now we are working on maybes, but I can tell you for sure, if my water is off for a couple of days, my crops are going to die," said Luke Petersen, who farms 100 acres in Salt Lake County. "I don't need a team of scientists to tell me my crops are going to be dead in a few days."

Petersen, a canal user, is scrambling to find an alternative source of water.

State water officials say regardless of how long secondary water is off, people should refrain from "cross connecting" those idled systems to their culinary water. The act is illegal and could spread contamination to drinking water.

Algal blooms are caused by excess levels of phosphorus and nitrogen.

Baker said the Utah Lake bloom was caused by too much phosphorus, which will be subject to numerical limits imposed on wastewater treatment plants by the state starting in 2020.

Of the seven plants that discharge into Utah Lake, only the Orem facility is currently meeting the limit, Baker said.

The division, coincidentally, is hosting a 2 p.m. Tuesday meeting on its water impairment report released last month that named Utah Lake to its list because of its nutrient pollution. The meeting is in its board room, 195 N. 1950 West. The state is aslo posting updates on its website.

Baker said it is impossible to say how long the bloom will last. A number of conditions — such as a rainstorm — could chase it away, but that won't address the overall nutrient pollution problem.

"If there is resistance to making these improvements in wastewater treatment plants, this recent event illustrates and presses the need to take some action," he said. "This was not a surprise. This was a matter of when it was going to happen, not if it was going to happen."

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