Early in the afternoon on July 4th, many people in the St. Croix Valley began to notice a haze in the air – and not from the fireworks. In fact, the smog-like air was actually the result of smoke drifting down from forest fires burning in Canada, more than 1000 miles away. By Monday, July 6, a storm system pulled the smoke even deeper into Minnesota, prompting the Minnesota Pollution Control Agency (MPCA) to declare the air “unhealthy” for everyone – not just children, elderly people, and those with breathing problems. On an air-quality scale that ranges from 0 to 200, some parts of Minnesota, including the Twin Cities, rated in the 170s and 180s, close to the worst ever measured in Minnesota. The Associated Press reported that smoke reached as far south as Tennessee, with a thick haze extending through much of North Dakota, South Dakota, Minnesota, eastern Nebraska, Iowa, Illinois and Missouri.
Strange as it may seem that smoke from Saskatchewan can travel as far away as Minnesota, the phenomenon has been a visible reminder that air, like water, refuses to follow political boundaries.
In addition to monitoring air quality, the Minnesota Pollution Control Agency also keeps track of lakes, rivers and streams in the state, noting which are safe to swim in and fish from, and which are impaired due to pollution. Of the water bodies classified as impaired in Minnesota, two-thirds suffer from mercury contamination, including 1250 lakes and river stretches in which the fish have elevated levels of mercury in their tissue, and 22 in which the water itself has unsafe levels of mercury. As a result, the Minnesota Department of Health has created fish consumption guidelines for how often certain fish from impaired water bodies can be safely eaten. Even some of the most pristine wilderness lakes in the Boundary Waters suffer from mercury contamination. Where is the mercury coming from?
It turns out that atmospheric deposition (mercury in the air that falls down onto the land and water) supplies more than 99.5% of the mercury getting into fish. MPCA research has determined that about 70% of this atmospheric mercury is coming from man-made sources, while the remaining 30% comes from natural sources such as volcanoes. Furthermore, about 90% of the mercury deposition in Minnesota originates from outside of our state. In other words, bad air in other parts of the world can translate into bad water here.
At the federal level, the U.S. Environmental Protection Agency is working to reduce mercury emissions across the country. Coal-fired power plants are currently the largest source of mercury emissions in the U.S., accounting for 25.4 tons of mercury per year being sent up into the air (49% of total U.S. emissions). Other large sources include electric arc furnaces used in steelmaking (about 10% of U.S. mercury emissions), industrial boilers (7%), and burning waste from the manufacture of Portland cement (5.5%). Globally, artisanal and small-scale gold mining is the largest source of man-made mercury emissions, followed closely by coal combustion. Other large sources include non-ferrous metals production and cement production. (United Nations Environment Programme, Global Mercury Assessment, 2013)
When it comes to protecting communal resources like air, water, forests and wildlife, we often realize quickly that many problems cannot be solved entirely at a local level, though it’s important for us all to do our part. Like the smoke from a wildfire, air and water move without regard for our borders and lines.