Steffan Browning from the fumigant action group said the group wanted any fumigants recaptured after being sprayed and dedicated facilities for fumigation to be carried out in.
"We don't know what the issues are with toxicity. We've heard some evidence but there's a whole lot of unknowns.
"I've got no doubt about the need for this type of chemical. Yes we need them but we've got to use them safely.
"We oppose EDN on the basis we're not confident there's enough information about it."
Browning brought up a March incident when four port staff, who were working 100m from where stacks of logs were being fumigated with methyl bromide, fell ill.
An investigation later found there was insufficient evidence to support claims methyl bromide exposure was to blame for the illnesses.
Chairman of the decision-making committee Dr John Taylor said the hearings were about seeing if the chemical was suitable for the purpose requested by the applicant.
"We can enter some more specific negotiations to resolve scientific difficulties which are at the heart of the decision we're making."
A final decision on the application will usually be made within 30 working days.