Phosphorous has long been recognized as the nutrient that promotes excessive aquatic plant growth and pollution of lakes. This often results in matting, algal blooms, invasion of undesirable species, with displacement of desirable native species and major impacts on recreational uses of lakes.

In the early 1970s, Michigan took major steps towards control of phosphorous in state waters through passage of the Cleaning Agents Act and the accompanying administrative rules. The rules established a limit on phosphorous content in laundry detergents of 0.5%. The soap and detergent industry vigorously fought the limit in the administrative and judicial arenas, arguing that no other compounds could provide adequate cleaning ability, and other materials would be highly corrosive and destructive to washing machines.

History has proven these arguments false. The limit has allowed both septic systems and wastewater plants to function far more efficiently. Improvements in water quality have been seen statewide, with numerous inland lakes and the waters of the Detroit River flowing from Detroit to Lake Erie serving as prime examples. Phosphorus levels at most southern Michigan river mouths fell by more than 70% after the detergent limit was enacted.

Due to a loophole in state law, dishwashing detergents are capped at 8.7% phosphorus content-more than 17 times the limit in laundry detergents. In the 1970s, most small lake cottages did not have dishwashing machines. But today's lakeshore has typically been converted from small cottages to year-round homes, which possess dishwashing machines. These are probably used daily, providing loadings to septic or wastewater systems in excess of the laundry machines. During my career with DNR/DEQ, I supervised enforcement of the Cleaning Agents Act, and while there were violations of the laundry detergent limit, even more regrettably, department management displayed no interest in toughening the dishwasher detergent limit.

So what can we each do? Most immediately, you can check labels of dishwashing products for phosphorous content and select the lower level products. You will probably change to a liquid product since these clean well and have only about 1.5% phosphorous compared to the approximately 4.0% to 7.0% in gel and powder forms. Equally important, you can contact your legislators and the Department of Environmental Quality and urge a change in Michigan laws to have dishwashing products also limited to 0.5% phosphorous, which will provide better water quality in Michigan waters.

Dennis Swanson served 28 years in the water quality programs of the Departments of Natural Resources and Environmental Quality before retiring in 2000.