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This page provides information on what odour is and how it affects people and the environment.

This page has not yet been updated to reflect changes as a result of Our air 2018 report.


Odour is a sensory response to the inhalation of chemicals. When the sensors in your nose come into contact with an odorous chemical they send a signal to your brain which interprets the signal as an odour. The human sense of smell is very sensitive to a wide range of odorous chemicals.

Pigs aren’t necessarily smelly
but pig farms can be if not
properly managed.


Odours are caused by mixtures of chemical compounds. 

They come from a wide range of sources such as:


garden compost heaps silage
landfills car and bus exhausts
mushroom farms pig farms

Effects on people and the environment

Odours in the environment are mainly a nuisance as they affect enjoyment of the outdoors. In more serious cases they can lead to sickness (eg, nausea and headaches). People’s response to odour varies (eg, people who live and work in rural areas may not be affected by silage smells while urban dwellers may find them offensive).