2.4 Public health and sustainability  (Page 4/12)

The reduction of extreme cold due to global warming, could reduce the number of deaths due to low temperatures. Unlike for heat, those deaths are usually not directly related to the cold temperature itself but rather to influenza. Also, deaths related to cold spells would increase to a lesser extent by (1.6%), while heat waves increase them by 5.7%.

Since volatile organic compounds    are precursors of ozone, and VOC emissions increase with temperature, this could lead to an increase in ozone concentrations. For fifteen cities in the eastern United States, the average number of days exceeding the health-based eight-hour ozone standard is projected to increase by 60 percent (from twelve to almost twenty days each summer) by the 2050s because of warmer temperatures ( Lashof,&Patz, 2004 ). Pollen levels may increase with increased CO ₂ levels since that promotes growth and reproduction in plants. This will increase the incidence of allergic reactions. Similarly, poison ivy will grow more and be more toxic.

Infectious diseases are influenced by climate as pathogen survival rates are strongly affected by temperature change. Diseases carried by birds, animals, and insects (vector-born) – such as malaria, dengue fever, and dengue hemorrhagic fever – may be influenced by temperature as mosquitoes are sensitive to climate conditions such as temperature humidity, solar radiation, and rainfall. For example, there has been a strengthening of the relationship between the El Nino global weather cycle and cholera outbreaks in Bangladesh. Increases in malaria in the highlands of eastern Africa may be associated with local warming trends. Temperature also affects the rate of food-born infectious disease. In general, however, it is hard to isolate the effects of climate change that affect the transmission rate and geographic boundaries of infectious disease from other social, economic, behavioral, and environmental factors (see McMichael et al., 2006 ). Increased precipitation from extreme rainfall events can cause flooding which, especially in cities with combined sewer and stormwater systems can be contaminated by sewage lines. This can happen when the deep tunnelsthat carry stormwater in Chicago reach capacity and untreated sewage then must be released into Lake Michigan. E. Coli levels in the lake then increase, forcing beaches to close to prevent the spread of infection.

Diseases are re-emerging and emerging infectious due to intensified food production in “factory” farms. Examples include mad cow disease (1980s in Britain); the encroachment on rain forest by pig farmers exposed pigs and farmers to the “Nipah” virus carried by rainforest bats that were seeking food from orchards around the pig farms – driven by deforestation and the drought of El Nino. This caused infection of pigs which lead to human illness and more than one hundred deaths. Poultry farming (avian influenza viruses) - crowded ‘factory farming’ may increase the likelihood of viral virulence when there is no selective advantage in keeping the host bird alive. Other food related issues are discussed in the next section.