The situation in North America
In the United States, the Environmental Protection Agency (EPA) does not regulate odour as a pollutant; therefore, odour regulations are often found within specific states and local jurisdictions. For individual states, state departments are in charge of enforcing odour rules or regulations issued by state legislatures. In the absence of odour regulations, citizens and communities can use basic “common law” nuisance lawsuits. However, exclusions and exemptions, such as “right-to-farm” laws and vague definitions of “nuisance”, can sometimes make nuisance actions difficult and expensive to prosecute.
As of 2018, odours were most commonly regulated through the method of field olfactometry. Ten states currently utilise a Scentometer (D/T method) field olfactometry limit for their odour regulation: Colorado, Connecticut, Delaware, Illinois, Kentucky, Missouri, Nevada, North Dakota, West Virginia and Wyoming.