Workers exposed to potential poisons during the clean-up of a toxic waste site at Mapua near Nelson may have long-term health issues, a new report warns.
The health of at least four workers was damaged during the clean-up which ended in 2008 and all 30 workers are being contacted and offered free medical assessments.
The Department of Labour report says some hazards were not recognised and workers could have been exposed to toxic substances including evaporating pesticides, dioxins and benzene.
The report's author, David McBride from the University of Otago, says health and safety plan for the plant changed as work progressed because there were teething problems with experimental cleaning processes used.
The department says it is acting on the report's recommendations and has started updating guidelines for toxic clean-ups.