Protestors called on Wellington's regional council on Monday to more tightly control methyl bromide at the city's port.
The gas is a fumigant and is mainly used at ports to ensure export logs are free from pests.
The newly-formed Coalition Against Methyl Bromide says methyl bromide has also been linked to respiratory and neurological problems in people exposed to it in large quantities.
Green Party health spokesperson Sue Kedgley says changes need to be made now.
She says everyone within the vicinity of fumigation areas is at risk and viable alternatives are available.