Housing has an impact on health and well-being through numerous environmental pathways. Key housing related environmental health risks include: 

• household air pollution from cooking, heating and lighting, particularly rudimentary biomass and coal cooking and heating stoves; 
• indoor air quality risks from dust or gases emitted by toxic building materials or radon exposures;
• exposure to extreme heat and cold;
• exposure to disease-bearing vectors, including pests and insects;
• exposure to damp and mould;
• lack of access to clean drinking-water and sanitation;
• outdoor air pollution – both from household emissions and other sources;
• urban siting and design features, which affect exposures to flooding and extreme weather; access to green spaces for physical activity; noise exposures; and access to transport routes;
• use of unsafe construction materials and poor construction practices. 

These environmental factors impact on a range of disease and disability conditions, including: 

• airborne infectious diseases, including TB; 
• vector-borne diseases (e.g. malaria, Chagas, leishmaniasis);
• waterborne/diarrhoeal diseases related to unsafe water and sanitation;
• noncommunicable diseases, including risk of stroke, heart failure and other cardiovascular diseases (from air pollution as well as extreme temperature exposures;
• allergies (from mould and damp); and cancers, e.g. from radon exposures;
• domestic injuries;
• mental health and neighbourhood social cohesion;
• occupational health risks, ranging from injuries and falls to environmental exposures to toxic building materials. 

The use of traditional fuels for household cooking, heating and lighting is also associated with a high risk of burns (e.g. from children falling into fires, spilled fuel, etc.) and poisoning (e.g. from children ingesting kerosene). Women and children may also be at risk for injury and violence during fuel collection. Fuel gathering may take many hours per week, limiting other productive activities and taking children away from school. Reliance on wood as fuel can also contribute to deforestation, especially in areas where fuelwood is scarce. Unsustainable wood harvesting can lead to forest degradation and loss of habitat and biodiversity. 

In terms of heating systems, portable kerosene cookers and heaters emit significant particulate matter, including black carbon emissions, directly into the household environment, or outdoors. Portable gas heaters emit comparatively less particulate matter, but can still release excessive quantities of NOx into the indoor environment; they also pose risks for carbon monoxide poisoning. 

Central heating systems, in which fuel is burned in a contained boiler to heat water or another circulation liquid, usually provide a clean indoor environment. However, systems that burn diesel or fuel oil tend to release significant particulate matter outdoors – contributing to ambient air pollution as well as to climate change – through both CO2 and black carbon emissions. Central heating systems that operate on natural gas or liquefied petroleum gas fuels generally emit far less particulate matter, including far less black carbon, as well as lower CO2 emissions. 

• Moisture build-up, mould and bacterial growth can occur as a result of structural building faults, inadequate heating, insulation or inadequate ventilation. These can increase risks of allergies and asthma. 

• Radon is a radioactive gas that emanates from certain rock and soil formations, concentrating in the basement or ground levels of homes, in the absence of inadequate ventilation or evacuation systems. Recent studies on indoor radon in Europe, North America and Asia indicate that lung cancers attributable to radon may range from 3–14%. 

• Asbestos fibres, used in roofing and insulation, have significant carcinogenic effects upon exposed building inhabitants and construction workers. Asbestos use is still unregulated and prevalent in many developing countries. 

• Lead, still common in certain paints and pipe products in developing countries, has toxic effects and exposure to inhaled or ingested lead dust from has been linked to impaired childhood cognitive development. 

• Volatile organic compounds (VOC), including formaldehyde, may be emitted slowly from indoor building materials, furniture, paints and carpets. VOCs also may be released by smoking and detergent, or drift in from attached garages or outdoor sources. These can contribute to acute conditions (e.g. poisonings) as well as cancers and asthma. Compact fluorescent lights as well as thermostats commonly contain mercury and thus must be handled with care to avoid exposures, particularly when broken. 

  Risks of indoor air pollutants can be lowered by adequate natural ventilation as well as through the use of healthier building materials, including replacement or phasing out of hazardous building substances wherever possible.