Workers exposed to dioxin during the manufacture of phenoxy herbicides at the Ivon Watkins-Dow plant in New Plymouth are more likely to die from cancer, a new study from Massey University shows.
The company - now Dow AgroSciences - made the pesticide 2,4,5-T at its New Plymouth plant from 1960 untilthe 1980s.
In the study, 1025 production workers at the IWD plant and 703 sprayers were followed up over a 30-year period.
When compared with the general population, there was no increase of cancer among the sprayers, yet there were higher mortality rates from cancer among the production workers, particularly those in jobs with likely dioxin exposure, said Professor Neil Pearce, from the university's centre for public health research, in a statement.
The study was conducted as part of a World Health Organisation-run international study, and presented at an international symposium on occupational health in Melbourne.
Professor Pearce said the findings of Massey's study were consistent with the WHO study, which involved 22,000 workers in 36 plants in 123 countries.
"The WHO study found that production workers exposed to dioxin had a 29 per cent increased risk of cancer. In New Plymouth we found a 24 per cent increased risk, which is very similar, particularly when we take into account the small numbers involved," he said.
The study follows the release of an interim study by the Ministry of Health, which revealed on September 9 that tests had shown some long-term residents in the New Plymouth suburb of Paritutu had a higher than normal level of dioxin in their blood.
The report on the blood dioxin study of 24 residents said the higher levels were most likely to be from breathing emissions originating from the Paritutu plant.
The ministry has still to test levels of former workers at the plant.
Professor Pearce said although blood tests had not been done on the former workers, their levels of dioxin exposure were probably much higher than those in the community, so any cancer risk in the community would be much lower than that of former workers.
Chlorophenoxy herbicides were produced and used widely in New Zealand from the late 1950s until 1987.
