The Green Party says port workers may have been exposed to dangerous levels of a toxic chemical.
A report released by the Customs Service reveals that 90% of shipping containers sampled at the Port of Tauranga had methyl bromide in the air, with 18% of these above safe levels.
The poisonous chemical is used to fumigate containers arriving from overseas.
Green Party biosecurity and customs spokesperson Steffan Browning says it is appalling port workers were not alerted to the potential exposure.
Mr Browning says methyl bromide has been linked to motor neurone disease and cancers.
He said the Customs Service needs to urgently act to ensure ports have the ability to recapture methyl bromide in shipping containers.
The Customs Service did not respond to a Radio New Zealand request for comment.