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“We were quite surprised,” said Dr. Gerry Schwalfenberg, the Edmonton physician who co-authored the research. “If you drink three or four cups a day, which a lot of people do, you’re getting too much [lead] for baby.”

Representatives of the Tea Association of Canada could not be reached for comment on the study, published in the Journal of Toxicology.

The findings do sound plausible, though, considering that China burns an “enormous” amount of coal, said Gideon Forman of the Canadian Association of Physicians for the Environment.

“Lead is a brain poison and that’s a big public health concern,” said the Mr. Forman, the group’s executive director. “To hear that there is a new route to exposure, something that people are ingesting, is very troubling.”

The study has some methodological problems, and there is too little evidence to argue the lead does mostly comes from Chinese coal plants, said Michael Brauer, a University of British Columbia expert on air pollution and environmental health. The results appear to make sense, however, given previous research, he said.

“I don’t think there’s cause for alarm,” said the UBC professor. “[But] if you drink a lot of tea when you’re pregnant, that’s probably not a good thing, and there doesn’t seem to be a lot of rhyme or reason as to which teas are higher or lower.”

The threat from lead poisoning — which at extreme levels can cause coma and death — has shrunk considerably in the past few decades, after the metal’s use in paint was curtailed in the 1950s and later banned, and leaded gasoline phased out in the 1980s.