According to the latest Environmental Protection Agency data, harmful algae bloom events are increasing across the country - including in Wisconsin.
In 2021 more than 100 people were sickened by toxic algae, mostly in freshwater, and the number of reported toxic algae outbreaks have increased each year from 2015 to 2023.
John Rumpler - clean water director with Environment America, the group behind the analysis - said nitrogen, phosphorus, grease, bacteria, and other farm runoff are driving factors.
"These industrial scale operations with hundreds of dairy cows or thousands of hogs," said Rumpler, "that volume of manure, whether it's spread on crops or otherwise managed, it just all too often winds its way from the croplands to rivers and lakes and streams."
Exposure to toxic algae can cause skin rashes, headaches, vomiting, pneumonia and more in humans, according to the EPA. Children and pets are especially vulnerable.
In the new Census of Agriculture, data show the number of Wisconsin farms is declining, but farm sizes are growing - underscoring concerns about the expansion of industrial agriculture
Rumpler added that, in rural areas, slaughterhouses are also triggering blooms.
"It turns out that slaughterhouses, the places where a lot of these animals are brought to be turned into hamburgers or chicken nuggets or even pet food," said Rumpler, "they also release a huge amount of nitrogen and or phosphorus into our waterways."
Federal regulations for slaughterhouses haven't been updated in twenty years, and not since the mid-1970's for smaller facilities.
Rumpler said it's encouraging the EPA is now considering new changes to its rules, largely in response to advocacy groups.
"EPA estimates," said Rumpler, "the strongest version of what they're considering would reduce slaughterhouse pollution, including nitrogen and phosphorus, by 300 million pounds a year."
