(Originally published in Intervenor, the CELA newsletter until 2004.)
Intervenor: vol. 27, no. 1 – 2, January – June 2002
By Linda Pim, Kathleen Cooper and Karyn Keenan
Swirling amidst the debate on pesticide bylaws for Canadian municipalities are plenty of numbers purporting to compare urban with agricultural pesticide use.
Some representatives of the chemical lawn-care industry belittle the public concern about urban pesticide use, arguing that a far greater tonnage of pesticides is used on Canadian farms than on urban lawns and gardens, as well as on golf courses. While arguing that urban pesticide use is relatively minimal, industry spokespeople also vigorously fight the passage of municipal pesticide bylaws, citing business losses, among other concerns.
While the total amount of pesticides used in Canadian agriculture is indisputably and significantly higher than the total urban use, what really matters for human health is the intensity of pesticide use – the kilograms of pesticides used per hectare (kg/ha) of land per year. Intuitively, one would expect that pesticide exposure would be higher when the spraying is occurring literally right outside the door, along the street, and in parks and school grounds. One would expect that exposure that is closer at hand and on surfaces with which people can come into direct contact (notwithstanding signs that children, pets and wildlife might not be able to read) would be higher than exposures resulting from agricultural uses. In trying to determine if exposure from urban uses is different, we have found that the numbers vary and information sources, when available at all, are conflicting.
Here we present numbers gleaned from provincial government sources and invite others to confirm or challenge the range of pesticide use intensity that we have calculated.
At a November 2000 conference in Banff on weeds, Janet McLean of Alberta Environment made a presentation called “Pesticide Use Across Different Agricultural Sectors”. McLean reported that in 1998, urban residential pesticide use intensity in Calgary was 2.92 kg/ha, while agricultural use was 0.8 kg/ha. In other words, 3.65 times more pesticide was used per hectare in urban settings than in agriculture.
However, the Alberta data alone is not representative of all of Canada, since most farm pesticide use in that province is for grain crops. Pesticide use is not nearly as high on conventionally grown (non-organic) grains as it is on conventionally grown fruits and vegetables.
We then looked at 1998 data from the Ontario Ministry of Agriculture, Food and Rural Affairs. The total tonnage of agricultural pesticide use for that year was 5,200 tonnes or 5,200,000 kg. The total crop acreage in 1996 (the year closest to 1998 for which census data are available) was 3,504,000 ha. Therefore, Ontario farm pesticide use amounted to 1.48 kg/ha.
With the reasonably safe assumption that urban residential pesticide use in Ontario cities and towns is approximately the same as that given for Calgary by Alberta Environment, we calculate the Ontario urban versus agricultural use as follows: 2.92 kg/ha (Alberta urban residential) divided by 1.48 kg/ha (Ontario agricultural) equals 1.97 times more pesticide used per hectare in urban residential than in farm settings. The difference between the Alberta and Ontario figures is accounted for by the far higher production of fruits and vegetables in Ontario than in Alberta. In order to err on the side of caution, we have calculated the range of difference in pesticide use intensity: 1.97 to 3.65 times more pesticide is used by weight per hectare per year in Canadian urban residential settings than in Canadian agricultural settings.
This is but one set of calculations aimed at trying to pin down the intensity of pesticide use. Our conclusion: The above calculations demonstrate that urban pesticide use is, indeed, more intense than agricultural use. We could not find out whether the original risk assessment calculations considered the higher intensity of urban use in setting maximum residue limits. We do know, however, that children were not accounted for in these original evaluations. This fact is one reason that lawn and garden pesticides are the subjects of re-evaluation.
It seems reasonable to conclude therefore, that for those pesticides approved for both agricultural and urban use, the higher intensity of urban use will contribute to higher risks of exposure and health effects in urban areas. Greater risks may also arise from the high rate of violations reported during inspections of the pesticide applicator sector by the Ontario Ministry of the Environment (MoE) (see Related Information here). We welcome additional data from others who may be able to confirm, refute or refine our numbers.
Linda Pim is conservation policy coordinator at the Federation of Ontario Naturalists. Kathhleen Cooper is a researcher at CELA. Karyn Keenan is a lawyer working on special projects.