Ask TreeHugger: What's the Dirt on Phosphate-Free Soaps?

algae bloom in a pond

David Pardoe / Getty Images

Question: Why is it so important to use phosphate free soaps? Is there a difference in how they work? They don't seem much more expensive, but is there a catch? Also, why aren't all soaps phosphate free? We know it is possible since there are many on the market, and we are told that they are better for nature. So why still make the more harmful soaps?

Response: Phosphorus, generally in the form of phosphates, has historically been one of the main ingredients in detergents (which are soaps made from synthetic materials). In the detergents, phosphates served as a "builder" to improve the detergent's cleaning efficiency. Builders, such as STPP, are important to the cleaning process, as they help to remove dirt from the clothes and to minimize soap scum (often seen as a ring on the tub, washing machine, or shirt collars). The need for builders in detergents and soaps is especially important in areas with "hard" water that contain calcium and magnesium ions, since the builders prevent these ions from interfering with the cleaning process.

High Levels of Phosphates Lead to Excessive Algae Bloom

Of the detergent builders, phosphates were the most popular, because of their superior cleaning performance. Their strong cleaning performance, however, has increasingly been overshadowed by their harmful effects on rivers, lakes, streams, and other fresh waters. Levels of phosphates in these fresh water bodies can be much higher than normal as the result of contamination from municipal and domestic wastewater that contains phosphates -- some or much of which (depending on your perspective) comes from phosphate-containing detergents that go down the drain after use. Although phosphates are an important plant nutrient, higher than normal phosphate levels can destroy the health of the lake, stream or other fresh water body, as they allow algae in the water to grow faster than would naturally occur, turning clear lakes and rivers green and cloudy. This extra algal growth is not only unappealing to look at, but can also make the water smell bad and make it unsuitable for swimming. It can also make drinking water more expensive to filter and can spoil the taste or smell of the drinking water.

In the long run, the excess algal growth can have devastating impacts on the health and age of a fresh water lake or river, causing eutrophication to speed up, where lakes and other water bodies fill in with dead algae and other organic matter and eventually turn into dry land.

Some Countries Have Banned Phosphates in Laundry Detergents

Given these harmful effects, laws or regulations were enacted in many U.S. states, the European Union, Canada, and in Japan to limit or ban the use of phosphates in laundry detergents. These limits and bans likely had the added benefit of convincing laundry detergent makers to replace phosphates from their products with non-phosphate alternatives, such as zeolite A, sodium carbonate, citrates, and sodium silicate. Although not in use in the United States, Canada, Japan, and many Western European countries, phosphate-containing laundry detergents are still used in many other countries.

Regulation of Phosphates in Dishwasher Detergents

Recently, some governments have also begun to look at regulating phosphates in automatic dishwashing detergents, which can contain anywhere from 4-8% phosphorus. Beginning in the middle of next year, for example, the State of Washington will gradually put in place a phosphate ban for dishwashing detergents in an effort to protect the Spokane River. Whether more state and federal governments will follow Washington's example is not clear, although groups are working to see that it happens.

Phosphate-free Dishwasher Detergents

In the meantime, you could on your own choose to use automatic dishwasher detergents that do not contain phosphates. The March 2005 issue of Consumer Reports rated phosphate-free dishwashing detergents, with several brands rated highly including Seventh Generation, Ecover Natural and Trader Joe's brand.

Helen Suh MacIntosh is a professor in environmental health at Harvard University and studies how pollution behaves in the environment and how it affects people's health. Please keep in mind that her answers are just her interpretation of available information and should not be taken as the only viewpoint or solution to a problem. Use this column at your own risk.