Fertiliser company Ravensdown has been fined $1000 after an illegal discharge of sulphur dioxide earlier this year.
The penalty came with an infringement notice issued by the Hawke's Bay Regional Council after the discharge exceeded allowable limits in April.
A council spokesperson said the council operates an air quality monitor at Awatoto to measure concentrations of particles in ambient air in this industrial and coastal area.
The monitor could detect pollutant particles emitted from industry as well as windblown dust and sea salt.
In one hour-long period in April the sulphur dioxide averaged 620.5 micrograms, exceeding the National Environmental Standard by 50.6mcg.