Troubled Waters

Common contaminants and pollutants

Something’s in the water. Actually, many things are, and not all of them should be. 

Here are some of the most common contaminants in Wisconsin’s surface water and groundwater, as well as where they come from and why they’re cause for concern, according to the Wisconsin Department of Natural Resources (DNR). 

A comprehensive list of the state’s water contaminants can be found at

Surface Water Contaminants 

• Phosphorus, a necessary fertilizer for crop growth, has a major impact on Wisconsin waters, with small increases in phosphorus spurring significant aquatic plant and algae growth (and thus reducing recreational use, property values and public health.) Excess phosphorus comes from “nonpoint sources,” or runoff pollution; “point sources” like wastewater treatment plants; and natural sources like past phosphorus loads that build up in lake-bottom sediment. 

• Mercury can be found in most fish throughout the country, and the pollutant can build up in the bodies of people who eat fish and cause health concerns. Mercury occurs organically in rocks and soils, but it’s also released into the atmosphere via coal-burning power plants, some chemical-manufacturing plants and incinerators, and improperly-disposed products that contain it. It can travel long distances and settle directly on land and water when released into the air.

Sediment runoff – the loose sand, clay, silt and other soil that settles to the bottom of a water body – can smother aquatic breeding grounds, damage fish gills, worsen stream bank erosion and increase the risk of flooding by filling in stream channels. Two significant sources of sediment are improperly-managed construction sites and overgrazing livestock, which can trample streambanks and erode pastures.

• Chloride from road salt can impact drinking-water quality, harm fish and accelerate corrosion. Over time, elevated concentrations of it could potentially cause human health risks.

Groundwater Contaminants

• Biological hazards include bacteria, viruses and parasites, which can cause illnesses in humans. Animal waste and man-made wastewater are common sources of bacterial contamination. 

• Nitrate exposure at high levels can affect all humans – thyroid disease and an increased risk of colon cancer are two of the impacts, according to the Wisconsin Department of Health Services. Most well known is its ability to cause infant methemoglobinemia or “blue baby syndrome,” and other health threats to babies and pregnant people. It can enter the groundwater through fertilizers, animal-waste storage and feedlots, wastewater and sludge disposal, refuse disposal areas and private sewage systems.

• Pesticides can get into the groundwater through spills, misuse and incorrect storage and disposal, but they can also seep through via by-the-books field use. Many pesticides are carcinogenic and some can disrupt the endocrine system.

• Metals can find their way into the groundwater naturally or through human activities. Iron, for instance, occurs naturally, but cadmium and chromium result from metal-plating operations.

• Volatile Organic Compounds (VOCs) are found in gasoline, diesel fuel and industrial solvents, as well as household products like paints, drain cleaners and air fresheners. Long-term exposure to many VOCs is suspected to be carcinogenic, and short-term exposure to high concentrations can cause other health issues. Landfills, underground storage tanks and substance spills can introduce VOCs into the groundwater.• Emerging contaminants are substances that are increasingly evidenced in the environment and that could cause adverse effects for humans and the environment. Categories of emerging contaminants found in Wisconsin groundwater include Pharmaceuticals and Personal Care Products (PPCPs) and Per- and Polyfluorinated Alkyl Substances (PFAS), as well as agricultural and microbial contaminants.