Question to the Department for Transport:

To ask the Secretary of State for Transport, what assessment her Department has made of the potential (a) economic, (b) environmental and (c) health impact of a third runway at Heathrow.

An Appraisal of Sustainability and economic assessment were conducted before the Airports National Policy Statement was voted on by Parliament and designated in 2018.

https://www.gov.uk/government/collections/heathrow-airport-expansion#appraisal-of-sustainability-and-supporting-documents

Heathrow Airport Limited will need to provide an assessment of the impacts of any proposed scheme for a third runway, and provide suitable mitigations, as part of any Development Consent Order application. The Government would carefully consider any such application in line with the relevant policies and planning processes.