Modern laundry detergents no longer contain phosphates due to a ban passed in 1993. The law, however, did not apply to dishwasher detergents, many of which still contain phosphates; some states are moving to ban (or at least limit) phosphates in such detergents.
Until they were banned in 1993, phosphates were used in detergents as "builders." Builders support detergent action by softening the water (removing calcium and magnesium). Phosphates used as builders are generally classified as either orthophosphates or complex phosphates.
Phosphorus is one of the primary nutrients (along with potassium and nitrogen) for plant growth. When phosphates were used extensively in laundry detergents, the waste water carried the phosphorus to rivers, lakes, streams and ponds. This led to massive algae blooms--a condition known as "eutrophication." The algae depleted the water of oxygen, which resulted in the deaths of large numbers of fish and other organisms.
Prior to the ban, laundry detergents frequently contained between 30 and 50 percent phosphate builders. Intense debate among environmentalists, detergent manufacturers, and government officials began in the 1960s, and Congress enacted a ban that effectively removed phosphates from laundry detergents in 1993.
The laws that restricted the use of phosphates in laundry detergents did not apply to dishwasher detergents, and many such detergents still contain substantial percentages of phosphates. Some dishwasher detergent manufacturers, however, now offer "low phosphate" or "phosphate free" versions of their products.
In 2006, Washington state banned the sale of dishwasher detergents containing more than 0.5% phosphorus. At least eight other states are considering similar legislation.