Environmental Variables of Disease

What % of risk factor from disease is due to environmental factors?

70-90%

Climate

Precipitation and temperature- disease vectors e.g. malaria require high temps and standing water to breed. Higher temps can increase pollen→ allergies, asthma attacks, increase likelihood of food-borne vectors e.g. salmonella.

Extreme events e.g. heavy rainfall→ flooding → water-borne diseases.

Seasonality → SAD: seasonal affective disorder. Seasonal pattern of depression, usually in winter. Impacts areas in higher latitudes most e.g. 14% of population in Oslo, Norway.

Lack of sunlight→ vitamin D deficiency→ bone loss etc. Overexposure→ skin cancers.

Topography and drainage

Areas prone to flooding→ contaminate water supplies → waterborne diseases. Mosquitoes due to standing water.

Relief→ lower areas where water collects→ moquitoes.

Altitudes→ risks of skin cancer due to increased exposure to UV, locals have higher lung capacity.

e.g. LICs in Asia tend to have high density populations on flood plains of major rivers due to seasonal flooding for rice. However wet years→ unplanned floods. Contaminate freshwater supplies, create breeding grounds for mosquitoes. Hazards can displace people, impact roads and access to hospitals etc.

E.g. Haiti earthquake 2010→ 8500 deaths of cholera.

Air quality (problems- 2)

Burning fossil fuels→ gases, soot particulates. Long-term exposure→ respiratory problems, heart disease and types of cancers. E.g. China, air has visibly darkened with pollution. 1hr of exposure in urban cities→ 20minute decrease in life expectancy. Due to factory and car pollution. 2015- red alerts issued across 10 Chinese cities after smog blanketed the sky. Air pollution now linked to 3.7mn premature deaths globally in 2012.

Disproportionately affects low/middle income countries. Rural indoor air pollution in developing regions due to fuelwood and exposure to smoker increases risk of respiratory infections, lung cancer etc. Women + children at most risk. Household pollutants result in approximately **2.4** **billion** people being exposed to **dangerous levels**

Poor indoor air quality e.g. if not well ventilated→ mould, increasing risk of asthma attacks.

Air quality- solutions

Demands action of policymakers for supporting cleaner transport and energy. Rural air pollution tackled by reducing emissions from biomass energy systems, agricultural waste incineration etc. Indoor air pollution tackled by increasing ventilation and reducing exposure to smokers e.g. use of cleaner cookstoves.

Cleaner Cook Stoves (who, benefits, costs?)

Household air pollution kills more people every year than HIV and TB combined→ lung cancer, stroke, increased risk of pneumonia in children by 50%. Researchers at Envirofit designing clean burning stoves that reduce smoke and less use of firewood. Benefits: 80% less toxic emissions, consistent heating of food, reduced consumption of firewood, save up to 15% household income in developing regions, reduced time to gather firewood (social and economic benefits). Environmental benefits of reducing soot emissions, deforestation.

Can be a negative in some societies where smoke is used to keep mosquitoes away.

Water quality

WHO estimates 2mn deaths/year attributed to unsafe water and poor sanitation and hygiene. Estimated over 2bn people live in regions of water stress. Diseases include:

Diarrhoeal e.g. cholera due to inadequate drinking water. Malaria and water related vectors. Legionellosis (respiratory disease→ pneumonia) caused by contaminated aerosols by water sprays.

Due to contamination of human sewage, construction, irrigation and agricultural runoff, flood controls → standing water.

Water quality- solutions

Prevented by improving water supply, sanitation and hygiene. Progress made due to millennium development goals where 2.3bn people have since gained access to improved drinking water since 1990.

Better tools and procedures to improve water quality e.g. water safety plans.

Better education and awareness of contamination.

Availability of simple, inexpensive treatments and water storage systems at household level e.g. covering water storage.