The Ministry for Primary Industries says that methyl bromide is a "highly effective" fumigant used for treating products for export to control quarantine pests.
Of that, there's no doubt.
Doubtless too it's colourless, odourless, highly toxic to humans and damages the planet's ozone layer.
Last year, 118 tonnes of it was used to fumigate logs and containers at Napier Port.
Two things to bear in mind are that Napier's tonnage isn't high compared with other ports and, the arguments for retaining it as a biosecurity tool seem strong.