Because the sewage is diluted and disperses, regional health authorities say it is difficult to definitively link any particular instances of disease or infection to these discharges. But sewage carries pathogens — bacteria, parasites and viruses — as well as chemical toxins. The pathogens can cause infections, dysentery, and potentially even cholera. For high risk populations: children, the elderly and those with immunity—the result could be serious, even deadly.
An often-cited EPA estimate from 2004 concluded between 1.8 million and 3.5 million Americans get sick annually from recreational contact with sewage-contaminated waters.
Health authorities in Massachusetts closed public swimming beaches 915 times in 2011 because of high bacteria from stormwater runoffs and sewage overflows, an act echoed by other coastal states.
The problem persists because the goals of the Clean Water Act turned out to be far more costly than expected when passed in 1972.
At the time, two-thirds of the country’s lakes and rivers were unfit for swimming, according to 2002 congressional testimony. Today, that has been halved. The EPA estimates the federal government spent $61 billion on sewage treatment systems from 1972 to 1995.
The benefits are visible. The Charles River “really ran in colors” in the mid-1960s because animal body parts were dumped in the water from slaughterhouses, said Bob Zimmerman, executive director of the Charles River Watershed Association. Now, after an expenditure of $79 million, the Charles is now called the country’s “cleanest urban river,” Zimmerman said.
Boston Harbor was a cesspool four decades ago. After an expenditure of $5.5 billion dollars, construction of a new treatment plant on Deer Island in 1995 and a massive underground tunnel in 2011, the Harbor is much cleaner. Nitrogen overloads have plunged by 50 percent, oxygen has increased, and the sea grasses that once coated the harbor floor are returning, according to the Massachusetts Water Resources Authority.
But sewage pollution continues, in two ways.