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Farm Chemicals Threaten Our Air, Water: Scientists

Farming Biggest Source Of Pollutants That Kill Fish, Frogs

OTTAWA , 7:48 a.m. EDT May 1, 2001 --

Tom Spears, National Post

Twenty years after Lake Erie was revived from the dead, the fertilizer-based "nutrient" chemicals that killed it are again threatening Canadian waters -- and even the air, according to five federal departments in a report obtained under the Access to Information rules.

The pollutants kill fish and frogs. They acidify lakes and soil, just like acid rain. They are "on occasion, endangering human health."

The 235-page review was done by scientists from Environment Canada, Agriculture and Agri-Food Canada, Health Canada, Fisheries and Oceans Canada, and Natural Resources Canada, and obtained by Ottawa researcher Ken Rubin. The review, which took more than five years, was completed in January, 2001.

Farming -- especially the growing number of factory farms -- is the biggest source of these nitrogen- and phosphorus-based chemicals, the report says. Municipal sewers are big sources, too: Sewage treatment plants can kill the germs and remove the lumps, but cannot destroy all the chemicals in the mix.

The effects of this pollution are varied: Inland waters are choking in phosphorus until the fertilizer makes weeds and algae grow. As with Lake Erie, algae is more than a smelly, green muck: It can suck all the oxygen out of the water until fish die. Some blue-green coloured algae is toxic to the nervous systems and livers of fish and humans.

All over southern Canada, nitrogen contributes to acid rain, smog, and global warming as it mixes with other chemicals such as oxygen. It can make well water unfit to drink.

The effects on humans are uncertain, but the scientists are worried. In the lower Fraser Valley in British Columbia, ammonia from the manure in intensive farms forms a rural smog that bonds with acidic sulphates and other fine particles from vehicle exhaust and industry.

"Although its health effects are not yet fully known, the direct relationship between fine particles, respiratory disease and mortality has fuelled growing concern over this unusual phenomenon," the report says. The particles fall to the Earth or are washed out as rain, and enter the cycle again and again.

These pollutants are called nutrients because they cause plants to grow. Natural and necessary in limited amounts, they cause explosions of algae when they're dumped in large amounts, as in Ottawa's Rideau River. The report calls this stuff "algal scum."

Ottawa ordered the study after the Commons environment committee recommended regulating nutrients under Canada's toxic pollution law in 1995. The government asked: Are nutrients really a pollution problem? The short answer: Yes.

The report doesn't make recommendations for farming, sewage handling or other practices that relate to nutrients. However, it cautions that as our population grows, sewers discharge more waste and factory farms spread, the quality of our water will suffer without better pollution controls.

Among the report's findings:

- Factory farms are upsetting the balance of fertilizers in the soil, as farmers spread more manure than can be absorbed.

"In the high-intensity livestock areas of Canada, centred in Ontario, Quebec and Alberta, there are more nutrients available from manure than are required by crops."

- Farmers spread nearly two million tonnes of nitrogen in manure, sewage plant sludge and other fertilizers in 1996, and 441,000 tonnes of phosphorus. That's just the weight of those ingredients; the actual weight of the manure and other fertilizers was much more. These loads spill into waterways and kill fish, especially in the southern part of Ontario where factory pig farms are the big source.

- The rain and snow brought down 43,000 tonnes of nitrogen from industrial sources.

- Municipal sewage dumped 80,000 tonnes of phosphorus (one-fifth of the total from all sources) and 5,600 tonnes of nitrogen (nearly half the total) into lakes and rivers.

- While ammonia from a manure spill can kill fish suddenly, generally high nitrate levels are lethal to frogs and toads in a much slower way. "In areas of intensive agriculture in Southern Ontario, nitrate concentrations commonly exceed the Canadian drinking water guideline of 45 milligrams per litre" of nitrate in water, the report says. Yet even that "safe" level is up to four times higher than the level known to kill frogs in the lab.

-- Rachel Gibson (rgibson@hotmail.com), May 02, 2001