Sharyl Rabinovici (MPP’00), Don L. Coursey, and coauthors examine E. coli beach closings at the Indiana Dunes State Park

Beach closed again? Blame it on the birds. According to a DNA study released in February by the Lake County Illinois Health Department and Community Health Center, it now appears that seagull droppings were the number one cause of E. coli bacteria in Lake Michigan last summer. As we gear up for another summer on the beach, it might be beneficial to consider the effects of all those seagulls. But Don L. Coursey, an economist specializing in environmental policy, argues that, aside from one’s personal aversion to bacteria, it may make little economic sense, and probably little health sense, to close the beaches. And he has the data to prove it.

In a current study in progress, Coursey and his colleagues collected E. coli data and visitor statistics from the Indiana Dunes State Park from 1998 to 2001. Each week, officials take water samples to monitor bacteria levels. If the next morning, E. coli density exceeds the EPA standard, the beach is closed until a future sample registers as safe. A problem in these tests, however, is that the levels can vary widely from hour to hour, by location and depth of water. As such, there is little correlation between the readings from one day to the next. This may lead officials to inadvertently keep a beach open when it should be closed and vice versa. In fact, Coursey estimates that 14 of the 22 closures he examined were unnecessary, costing between $111,000 and $518,000. On the other hand, the swim area was left open 20 of the 28 days when E. coli exceeded regulations, costing a much more modest $1,658 to $6,661.

Add to this monetary cost the very low risk of contracting E. coli from swimming in a lake. Of the 777 E. coli infections nationwide in 1998, only 4 of the illnesses and none of the deaths were attributed to swimming in a lake. In fact, across the entire summer swim season in the Indiana Dunes State Park, the closure policy would prevent only 123 cases of E. coli, Coursey estimates. Meanwhile, visiting swimmers are denied a total of 17,820 days.

Of course this all changes if people suddenly place more value on health than past research has documented, or if they are especially averse to birds. A modest increase in the value of health in the authors’ calculations reverses their conclusion that leaving the beaches open regardless of E. coli levels makes more economic sense.

This paper, “The Economic and Health Risk Trade-Offs of Swim Closures at a Lake Michigan Beach” by Sharyl Rabinovici, Richard Bernknopf, Don L. Coursey, and Richard Whitman, is forthcoming in Environmental Sciences and Technology. For more information on the Lake County Health Department and Community Health Center or their study, visit them online at www.co.lake.il.us/health or contact Mark Pfister at 847-377-8028.