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Celebration of LifeArchive for Environment Canada
A case against arsenic-based pesticides
North America now has restrictions on harmful arsenic-based pesticides, thanks in part to four years of intensive research by a team led by Environment Canada.
The effects of these chemicals on human health, birds and insects only started to come to light after they were used to fight off an epidemic of mountain pine beetles in British Columbia’s forests.
The team was led by Dr. John Elliott, an EC research scientist who focuses on the study of ecotoxicology. Other members of the team included Dr. Christy Morrissey, a post-doctoral fellow, Dr. Bill Cullen, an international expert on the chemistry of arsenic, and other highly qualified biologists, chemists, summer students and interns from the University of British Columbia and Simon Fraser University.
The use of Monosodium Methanearsonate in BC
Monosodium Methanearsonate (MSMA) is an arsenic-based pesticide that was applied to treat trees affected by the worsening mountain pine beetle (MPB) epidemic in 2001. Frills were cut into the tree bark, and MSMA was injected underneath the bark to target the beetles. With this form of treatment, the beetles are killed — but so are the trees. The fatally infested tree is sacrificed in order to prevent further spread of beetles.
The pine forests of British Columbia’s central and southern interior have been devastated by the mountain pine beetle epidemic. To date, the area of pine trees that have been affected stands at 13.5 million hectares — about four times the size of Vancouver Island. The B.C. Ministry of Forests and Range projects that by 2013, 80 per cent of the pine trees in the affected area could be dead.
It is estimated that in B.C., during a 10-year period from 1995 to 2004, approximately 5080 kilograms of MSMA was applied to some 500,000 trees.
Investigating the impact of MSMA
In a research first, Dr. Elliott’s team found that woodpeckers feeding on the beetles had a significantly higher concentration of arsenic in their bloodstream. Prior to this project, a database allowing scientists to compare their findings did not exist.
The research took place during the 2004-2005 breeding seasons (April to July). The study evaluated the exposure of MSMA to woodpeckers, such as the Three-Toed and Hairy woodpeckers and other forest birds that lived within one linear kilometre of trees that had been treated with MSMA within the previous two years. The research team captured a total of 23 birds whose diets included a large component of beetles.
All beetles and bird blood samples were tested for arsenic. Beetle samples from MSMA treated trees contained high concentrations of arsenic. The blood samples collected revealed moderate but widespread exposure to MSMA.
The team concluded that under current environmental conditions, woodpeckers and other insect-eating species were being exposed to arsenic was occurring with the potential for significant consequences, such as weight loss and higher mortality rates.
While it was initially believed that MSMA was over 90 per cent effective at killing the beetles, the Environment Canada-led team found the success rate to be only about 60 per cent. Some beetles and larvae were still alive despite the application of the pesticide.
MSMA use in B.C. during the mountain pine beetle epidemic can be far-reaching. For example, carpenter ants feeding on dead trees can also serve as food for other species. As a result, the policy calls for ongoing research to determine the presence of arsenic in secondary insects.
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