Background
The built and natural environment and health are inextricably linked. However, there is considerable debate surrounding the strength and quality of the evidence base underpinning principles of good practice for built and natural environment design in promoting health. This umbrella review aimed to assess relationships between the built and natural environment and health, concentrating on five topic areas: neighbourhood design, housing, food environment, natural and sustainable environment, and transport.

We systematically review the impact of polyurethane insulation and polyurethane household products on the indoor environmental quality of buildings. The review breaks down polyurethane products into constituent compounds (isocyanate, polyol, flame retardant, blowing agent and catalyst) as well as secondary emissions, and discusses their implications on human health. Concentrations of compounds emitted from insulation, and household materials, measured in laboratory experiments and case studies are presented in the context of the built environment.