Community Garden Heavy Metal Study – Recommendations for Spring Gardeners
NSAC, Truro, NS — April 7, 2011 — Nova Scotia Agricultural College (NSAC) and the Ecology Action Centre (EAC) have released the results of a study looking at Heavy Metals in city garden sites in Halifax Regional Municipality (HRM). The study, funded by Environment Canada, HRM and NSAC, involved the sampling and analysis of soils collected from 26 community and private gardens, as well as 18 municipal public parks and lands across the HRM.
“We know that many urban areas in North America have been contaminated by past industrial practices such as the burning of fossil fuels to generate electricity and to heat homes, and the use of leaded gasoline,” explains Sadra Monfared, an engineer and the principal author of the report. “These metals can also occur naturally in soils, depending on the bedrock from which they are derived,” he added.
The question of soil health is an important one in the burgeoning urban gardening movement. The heavy metal study was to determine if soils in HRM were contaminated with lead, arsenic, copper, or zinc and to begin formulating recommendations for urban gardeners whose soils could be contaminated.
The study compared heavy metal concentrations found in the HRM soils to standards published by the Council of Canadian Ministers of the Environment (CCME). For soils used for agricultural purposes, the CCME limits for the concentration of lead and arsenic are 70 and 12 µg/kg (micro-grams per kilogram) respectively. Lead concentrations in the NSAC/EAC study ranged from 10 to 767 µg/kg, with an average lead value for all soils of 109 µg/kg. Approximately 40 per cent of the study soils exceeded the CCME guideline. Similarly, concentrations of arsenic in the soils ranged from 4 to 153 µg/kg, and approximately 50 per cent of the soils exceeded the CCME guideline. In the case of both lead and arsenic, most of the samples taken from the Halifax peninsula, where industrial activity has been going on for over 250 years, exceeded the concentration considered safe for agricultural use. At high enough concentrations, lead, arsenic and copper can be harmful to human and ecosystem health.
“Although there is a clear indication of elevated metals in these soils, we are still looking into what extent eating vegetables grown on affected soil is a hazard to human health,” commented Dr. Richard Donald a soil scientist at NSAC, and the technical advisor to the project.
The risk to gardeners is in ingesting lead from contaminated soils either through inhaling dust in the garden or from dirt on their hands travelling to their mouths. This is the most likely means of contamination rather than through eating vegetables grown in the soil.
“Based on past studies, and from consultation with health risk experts, we believe the risk to urban gardeners and to people who eat the vegetables grown on these gardens is low,” adds Dr. Donald. The authors of the report urge HRM gardeners, particularly those on the peninsula, to take steps to limit their exposure to heavy metals and the report offers several recommendations to mitigate these risks:
- Have your soil tested for heavy metals, organic matter, and acidity. This will help you decide what other precautions are needed, if any.
- Wash your hands well after gardening, or use gloves; rinse garden produce prior to eating; wash and peel root vegetables like potatoes and carrots and avoid weeding or digging dry dusty soil.
- Adding organic matter and lime to your soil will help to limit the uptake of metals by your body or by plants grown in the soil.
- If your site is highly contaminated, build raised-beds and import clean soil to isolate your garden from the contaminated area, or choose to garden elsewhere, such as your neighborhood community garden.
“It is not surprising, that in one of the oldest industrialized cities in North America, you would find contaminated soils,” says Garity Chapman of the Urban Garden Project of the Ecology Action Centre and an advisor to the study team. “We would like to encourage the growth of urban gardens as a way to promote food self-reliance and improve access to whole, nutritious foods. This is a community wide issue, affecting not only gardens but our green spaces in general. We need to care for our soil and do what we can to foster health and wellness in our cities,” she added.
The authors of the study feel it is timely, as many prepare for the summer gardening season that these concerns are made public. The Urban Garden Project will continue to look at this issue and offer support to the public as they build and work in their community gardens.
The complete study may be downloaded from the Ecology Action Centre’s website (http://www.ecologyaction.ca/content/urban-garden-project).
For further information or comment contact:
Carey Jernigan, Ecology Action Centre (urbangarden@ecologyaction.ca, (902-442-0202)
Dr. Richard Donald, Nova Scotia Agricultural College (rdonald@nsac.ca), (902-956-4925)
