People exposed to one of the world's worst industrial accidents, in which dioxin spewed out over the north Italian town of Seveso, face a higher risk of developing several kinds of cancer, a study said on Monday.
It added, though, that cancers unleashed by the toxic chemical had not surpassed expectations at the 30-year mark and the relatively small number of cases made it hard to pin down the size and pattern of risk.
Researchers led by Angela Pesatori from the Fondazione IRCCS Ospedale Maggiore Policlinico pored over the incidence of cancer among people who lived in Seveso at the time of the July 10 1976 disaster or who migrated there within the next 10 years.
They identified three areas of contamination: Zone A, where soil levels had a very high level of dioxin; Zone B, where levels were high; and Zone R, where levels were low.
Cancer numbers between these three zones were compared with those from a non-contaminated reference territory outside of Seveso.
A total of 2,122 cases of cancer occurred from 1977-1996, 660 of which occurred after 1990.
Zone A had a 40-percent increase in breast cancer among women, which is statistically not significant given that there were only five cases, but still warrants further investigation, the paper said.
Zones A and B also had higher levels of lymphatic cancer and leukaemia, but again, the statistical picture was clouded by small numbers.
No cases of cancer were found among the 183 who were diagnosed with chloracne, an acne-like skin eruption caused by exposure to the toxic chemical.
Most of these people, though, were young children at the time, and cancer is an age-related disease.
Dioxin has been classified as a human carcinogen by both the International Agency for Research on Cancer (IARC) and the US Environmental Protection Agency (EPA).
But whether exposure to it at Seveso would boost cancer prevalence has long been debated by scientists.
"We've found that it does pose a carcinogenic hazard, although lower than anticipated from animal studies, at least at the levels experienced by this population after this accident," Pesatori said in a press release, adding that "these increases were expected based on previous studies."
The paper appears in Environmental Health, an open-access journal published by BioMed Central.