Got an automatic dishwasher? You may be harming the planet with the soap you use in it.

So we can all welcome a bit of news lately about legislative action in Pennsylvania governing, of all things, that very soap.

For now, it contains phosophorus, which gets into waterways and, acting like the fertilizer that it's often a component of, causes blooms of algae and other aquatic growth. The plant life, in turn, sucks the oxygen out of the water and fish may die. Or mats of greenery on top of the water will kill everything underneath.

As usual: All sorts of problems when things get out of balance.

About two years ago when I was writing about the Wissahickon Creek, a Department of Environmental Protection official told me phosophorus was a big problem in the stream.

According to a 1998 study, the phosophorus content in some stretches of the stream was ten times above what a healthy stream should have.

To the algae of the Wissahickon, "it's like Thanksgiving dinner every day," the official said.

The DEP and the federal Environmental Protection Agency are looking at ways to control it.

The rationale is economic as well as environmental. Algae gives the water an "off" odor and taste, and the Philadelphia Water Department, which has a drinking water intake just below the Wissahickon's convergence with the Schuylkill, spends buckets of money — $200,000 or more — just to correct that aesthetic issue.

If phosphorus sounds familiar, it was banned from laundry detergents in Pennsylvania in 1989.  Why exempt dishwasher detergent? At the time there weren't many automatic dishwashers, and there were no economical alternatives to phosphorus in dishwasher detergent. So it stayed at levels of up to 8.7 percent — about the same as in a common houseplant fertilizer.

Recently, Pennsylvania Gov. Ed Rendell signed legislation banning it by July 1, 2010, except in detergents used in commercial or institutional dishwashers.

(Not to worry about the industry, which has already set corresponding voluntary standards, says Harry Campbell, a scientist with the Chesapeake Bay Foundation, which applauds the move because phosphorus is a huge issue in the bay as well. The legislation simply codifies the standard, he said.)

Meanwhile, elsewhere on the phosphorus front, back in April, New Jersey DEP commissioner Lisa Jackson signed a memorandum of understanding with members of the lawn-care industry, who pledged to reduce the amount of phosophorus released in fertilizers sold in the state. It's going down 50 percent by 2010.