Unpleasant, strong, long-lasting odours (smells) can become a problem if activities like industry, open landfills, wastewater treatment plants and rendering plants are not appropriately managed, particularly for people living nearby.

Complaints about odour emissions are one of the most frequent environmental pollution incidents reported to regulatory authorities. Approximately 11% of the complaints and incidents we received in the 2022-23 year were about odour.

Sources of odour in Otago could include:

• intensive indoor farming such as piggery and poultry farms
• stockpiles of organic waste on farmland
• agrichemical spray operations
• pulp and paper manufacturers
• commercial food processing and preparation
• meatworks and rendering plants
• commercial composting operations and landfills
• crematoriums
• wastewater treatment plants, pump stations and spray irrigation of effluent
• domestic sources, such as chimney smoke, outdoor burning, composting and house painting

Odours are caused by mixtures of chemicals that stimulate our sense of smell. Humans are very sensitive to a wide range of chemicals, and everyone reacts to odours differently. For example, someone who lives and works rurally may not be affected by silage smells while cityfolk may find them offensive. Some odours, like the smell of freshly mown grass, are pleasant while others are highly offensive.

An individual’s reaction can depend on the odour’s:

• frequency – how often it occurs
• duration and the time of exposure – for example, some odours may only occur during standard work hours, while others are more constant
• character and intensity
• location – for example, rural, industrial or public area

Sensitivity to odour can also vary depending on a person’s:

• age
• perception/view of the emitter
• mental state
• other compounding issues (such as stress at work or home)
• general state of health and wellbeing

Some odours are not culturally acceptable – for example, odours from a crematorium or wastewater treatment plant.

People can become de-sensitised to a smell over time and no longer find it offensive. For example, people who have grown up in a town where a particular industry is the main employer may generally accept those odour emissions as part of life.