CUPE Local 79, which represents about 20,000 city employees, says it is supporting the No Casino Toronto campaign.
Union president Tim Maguire said Tuesday a casino in Toronto could double the number of problem gamblers.
Maguire also pointed to a Toronto Public Health report that said the impact wouldn’t just be on the gamblers themselves — their families would also be negatively affected.
Toronto’s Board of Health voted against the proposed casino in February.
The board said that while some effects of a gaming facility — such as job creation — would be positive, most of the outcome would be negative.
Maguire says his members are also concerned about a negative impact on the community.
"Our members are front-line community workers in a city that’s already struggling under a social infrastructure deficit," he said. "We are worried that the social impacts of a casino could overwhelm Toronto’s already strained social support system."
The city’s plans for a casino hit a roadblock last month when Premier Kathleen Wynne said Toronto would not receive special treatment to help it host a casino, compared to other Ontario municipalities.
Earlier reports stated that the Ontario Lottery Gaming Corp. was offering the city as much as $100 million in hosting fees, a number that eclipses other municipalities.
Wynne said all municipalities must abide by the same funding formula.
Days after that conversation, the OLG said it was now considering Vaughan as well as Toronto, Mississauga and Markham-Richmond Hill for a southern Ontario gambling facility.
A vote by city council on whether to allow a Toronto casino is expected later this spring.