Suds, lather, and foam are brought to you by surfactants, ingredients that reduce the surface tension of water, both loosening and suspending dirt so it can be washed away. But when surfactants get into the parts-per-million range, they strip the protect-ive mucus from fish and attack their gills. Even parts-per-billion of nonyl-phenols, breakdown products from some laundry surfactants (now restricted in Europe), can disrupt endocrine function, resulting in, among other things, male rainbow trout with stunted testicles and females that neither forage effectively nor group together to fend off predators.

To help fish keep their wits (and testes), cottagers on the soft-water lakes of the Canadian Shield can take heed of a west-coast initiative: Cut back on soap and detergent. As with Lake Muskoka or Lake of Bays, two lakes with notably soft water, Vancouver’s soft water makes more foam with less soap, so “you only need a quarter or a third of the detergent you’d need in a hard-water area,” says Albert van Rood-selaar, division manager with Metro Vancouver’s Policy and Planning Department.

Warning sign #3: New mountain fresh fragrance!

Those “Alpine” scents more likely wafted in from a factory vat than the Matterhorn. In 2000, US manufacturers used 6,500 tonnes of synthetic musks in everything from soap to fabric softener. Based on samples from Lake Ontario’s Hamilton Harbour, one study estimates Hamilton-ians flush 98 mg per person per year of the common musk galaxolide into the lake. Those scents eventually settle into the lake bed. Sediment cores drawn from lakes Erie and Ontario during the ’90s and early this decade show the amount of galaxolide doubled in just eight years.

We know these artificial scents are building up in our lakes (as well as showing up in human fat tissues and breast milk) but sniffing out their environmental and health impact is more difficult. In the lab, synthetic fragrances weakened the cellular defences of mussels, and suppressed the natural estrogen production of female zebrafish.