One Year After Ontario Ban: Over 80 Percent Decline of Pesticides in Surface Waters

In April 2009, it became illegal to sell or apply pesticides for cosmetic lawncare in Ontario, Canada. It seems like a no-brainer risk versus benefits analysis: the benefit is ...hmmm, just cosmetic...while the risks are real, documented, and pervasive. But somehow the allure of a green, weed-free lawn keeps conquering rationality. A year later, does the preliminary data on the effectiveness of Ontario's cosmetic pesticide ban prove it is a good idea?

The scope of the pesticide ban is described on the News Ontario website:

Pesticides cannot be used for cosmetic purposes on lawns, vegetable and ornamental gardens, patios, driveways, cemeteries, and in parks and school yards. There are no exceptions for pest infestations (insects, fungi or weeds) in these areas, as lower risk pesticides, biopesticides and alternatives to pesticides exist. More than 250 pesticide products are banned for sale and over 95 pesticide ingredients are banned for cosmetic uses.

If you are a World Cup fan or a golf player, you might be asking yourself: but what about a perfectly groomed playing field? The Ontario ban provides for the continued use of some banned pesticides for special applications, under strict oversight of the Ministry of the Environment. Other exceptions include combatting poisonous plants or disease-carrying insects.

168 stream water samples were taken over 2008 and 2009, representing the water quality before and after the ban took effect. Sampling points were selected in areas mainly influenced by residential run-off -- away from golf courses, sewage treatment plant effluents, and agricultural applications. The samples were analyzed for 105 pesticides and pesticide degradation products.

The results are dramatic: three pesticides estimated to account for half of lawn care product applications dropped by 86% (2,4-D), 82% (dicamba), and 78% (MCPP: 2-methyl-4-chlorophenoxyacetic acid). On the other hand, concentrations of glyphosphate (Roundup) and carbaryl did not drop significantly. The results for glyphosphate (Roundup) are attributed to continued use of this pesticide in certain exempted applications. The carbaryl results are not explained; perhaps this is due to the persistence of carbaryl in sediment.

Continuing feedback on Ontario's "experiment" can only help support the use of alternative herbicidal treatments and the expansion of bans on cosmetic pesticides, as well as restrictions on the use volumes for other purposes. Well done, Ontario.