SAFE FOR SWIMMING?

Water around island varies

The St. Lawrence River is the lifeblood of our city, providing a commercial highway for shipping, drinking water and, for many, a recreational playground.

It has been heavily polluted, particularly during the 20th century. Some of the chemicals dumped in the river are still there, hiding in the sediment or making their way through the food chain to be ingested by birds or fish. The effects of other newer pollutants are little understood.

Though bacterium (fecal coliform) levels are the main indicator of whether an area is safe to swim in, experts suggest swimmers around Montreal avoid kicking up lake sediment or ingesting it.

The pollutants in the sediments off of Montreal can be divided into two categories: historical contaminants and emerging contaminants.

Historical contaminants are substances produced or discarded by industries along the river since as far back as the Industrial Revolution. They have been declining in most parts of the river, according to a 2014 overview of the state of the St. Lawrence conducted by the federal and provincial authorities.

But some areas remain contaminated, according to the report, including the southern part of Lac St-louis, the sector downstream from Montreal, Lac St-pierre and the ports of Montreal and Quebec City.

These contaminants include:

Polychlorinated biphenyls (PCBS), which were used in electrical equipment, paints, hydraulics and a myriad of other industrial applications before 1979, when they were banned in the United States. They cause cancer and have numerous other ill effects in humans.

Polycyclic aromatic hydrocarbons (PAHS), which occur naturally in coal, crude oil and gasoline, and are produced by the burning of many products. A February 2020 study concluded that they are toxic to aquatic animals.

Mercury, which has a wide variety of industrial uses but can cause kidney damage and induce a variety of other symptoms if consumed.

Researchers are only beginning to understand the effects of some new, “emerging” contaminants in the waterway. Their presence in the St. Lawrence is being increasingly monitored.

These include:

Polybrominated diphenyl ethers (PBDES), which have been used as flame retardants in a variety of plastics and textiles since the 1970s. Their sale and use has been prohibited in Canada since 2016. They can cause deformities and reproductive system problems in certain aquatic species.

Pharmaceuticals and personal care products (PPCPS). Chemicals found in medications and cosmetics eventually make their way into the river system. Hormones, particularly those given to animals on livestock farms, also make their way into the water. Water treatment plants don’t effectively remove them. These products disrupt the endocrine system of wildlife and may have other adverse effects.