A recent university study looking at soil at community gardens in Guelph found higher-than-recommended levels of contaminants like lead and arsenic at a small number of sites, but a city manager said the issues that were uncovered have already been dealt with.
The University of Guelph study by Asim Biswas and Fernando Montano-Lopez was recently published in the science journal Nature. Biswas is a professor at U of G and Montano-Lopez is an honours graduate student in the environmental sciences program.
“Guelph is a very family-friendly city and we like to walk on trails and do some other outdoor activities and I think gardening is quite a common one too,” said Biswas in a phone interview.
In 2018 the researchers took surface soil samples from 22 community gardens in the city, as well as samples taken from a greater depth. The testing found the soil at most of the community gardens in Guelph was within acceptable limits of heavy metal contamination as recommended by the Canadian Council of Ministers of the Environment (CCME).
“We analyzed the soil and used some other data to try to see how heavy metals are distributed across the city,” said Biswas.
The issues found in those community gardens as a result of that 2018 testing have already been dealt with, said Dave Beaton program manager of forestry and sustainable landscapes for the City of Guelph.
Two community gardens in the Ward — Huron Street Community Garden and Lyon Park Community Garden — were found to have higher-than-recommended levels of contamination.
The Huron Street Community Garden is located directly across the street from the former Northern Rubber Company building in an area of the city that was once more industrial. That building and the property around it are currently being developed for residential use.
The CCME limit established for zinc is 250 parts per million (ppm), but 17.5 per cent of samples taken across the city exceeded that number, with the highest found to be 546.67 ppm.
That site with the highest concentration of zinc was once the site of an industrial area of the city, which may be the cause for the levels recorded, said the study.
That site was also found to have a higher-than-recommended level of cadmium, a known carcinogen. Previous studies cited in the U of G study have shown eating lower levels of cadmium over long periods of time can lead to a build up of the substance in the kidneys and could cause bone to become fragile and break easily.
Fifteen per cent of sites showed an elevated level of lead, and one site surpassed the permissible limit for Arsenic.
Beaton said the issues were discovered prior to the U of G study when soil testing was conducted by the people operating the Huron Street Community Garden and confirmed by the city.
“When the situation was discovered at the Huron garden we then looked at results for all of the community gardens and discovered there was some contamination at the Lyon Park, so we brought that to the attention of those who had proposed the garden and we worked with them to come up with solutions,” said Beaton.
The community garden in Lyon Park was installed in 2015 and had been operating for a few years with the contaminated soil.
“The levels that we are talking about here, they are not in the high risk category,” said Beaton. “They are in the low to moderate category, and the size of the plots people are dealing with — these are not going to form a major portion of anybody’s diet. They are a supplementary component, so from a human health component, the impacts would be — I would imagine — be completely undetectable.”
Gardeners who were using the gardens in 2018 were informed of the testing results and the risks of growing food in those conditions.
Before the start of the 2019 growing season in those two gardens, a series of raised beds that were filled with clean soil and a barrier that prevents cross contamination.
“We have addressed it and people aren’t growing food in the community gardens in those soils,” said Beaton. “I feel a lot better with the situation as it is now and we have procedures in place now that it would never happen again.”
In the years since the the samples were taken, a number of new community gardens have popped up in Guelph, for a current total of about 30. That increase, said the study, shows the growing interest in Guelph to grow food locally.
“We have more community gardens than ever and for all of those gardens the soil quality all meets the standard,” said Beaton.
In many cases, said Biswas, community gardens are built in areas of the city with lower or middle incomes.
“Because they are in lower or middle incomes, they also like to grow their own food so they can financially support that monthly cost,” he said.
Those neighbourhoods which support people in lower and middle incomes have often been developed on land that was once zoned for industrial purposes, said Biswas.
“When we started looking at it, I had this hypothesis that as the city grows and develops, a lot of times we see an older neighbourhood is more expensive and when the newer neighbourhood comes up in the rest of the city, those tend to be on properties that were once used for industry,” he said. “Often we found home prices tend to be lower on those sites.”
When compared with census data, half of the community gardens in Guelph are located in areas of the city with the lowest incomes. Beaton said the gardens have filled a niche during COVID-19 with many community, economic and social benefits.
“They are servicing neighbourhoods where there are lower incomes and where people, in many cases, would benefit most from these,” said Beaton. “Going forward and currently those gardens are top quality. There was an issue and it has been addressed.”
