13.4.5 Human health
The regional assessments of health impacts due to climate change in the Americas show that the main concerns are heat stress, malaria, dengue, cholera and other water-borne diseases (Githeko and Woodward, 2003). Malaria continues to pose a serious health risk in Latin America, where 262 million people (31% of the population) live in tropical and sub-tropical regions with some potential risk of transmission, ranging from 9% in Argentina to 100% in El Salvador (PAHO, 2003). Based on SRES emissions scenarios and socio-economic scenarios, some projections indicate decreases in the length of the transmission season of malaria in many areas where reductions in precipitation are projected, such as the Amazon and Central America. The results report additional numbers of people at risk in areas around the southern limit of the disease distribution in South America (van Lieshout et al., 2004). Nicaragua and Bolivia have predicted a possible increase in the incidence of malaria in 2010, reporting seasonal variations (Aparicio, 2000; NC-Nicaragua, 2001). The increase in malaria and population at risk could impact the costs of health services, including treatment and social security payments.
Kovats et al. (2005) have estimated relative risks (the ratio of risk of disease/outcome or death among the exposed to the risk among the unexposed) of different health outcomes in the year 2030 in Central America and South America, with the highest relative risks being for coastal flood deaths (drowning), followed by diarrhoea, malaria and dengue. Other models project a substantial increase in the number of people at risk of dengue due to changes in the geographical limits of transmission in Mexico, Brazil, Peru and Ecuador (Hales et al., 2002). Some models project changes in the spatial distribution (dispersion) of the cutaneous leishmaniasis vector in Peru, Brazil, Paraguay, Uruguay, Argentina and Bolivia (Aparicio, 2000; Peterson and Shaw, 2003), as well as the monthly distribution of dengue vector (Peterson et al., 2005).
Climate change is likely to increase the risk of forest fires. In some countries, wildfires and intentional forest fires have been associated with an increased risk of out-patient visits to hospital for respiratory diseases and an increased risk of breathing problems (WHO, 2000; Mielnicki et al., 2005). In urban areas exposed to the ‘heat island’ effect and located in the vicinity of topographical features which encourage stagnant air mass conditions and the ensuing air pollution, health problems would be exacerbated, particularly those resulting from surface ozone concentrations (PAHO, 2005). Furthermore, urban settlements located on hilly ground, where soil texture is loose, would be affected by landslides and mudflows; thus people living in poor-quality housing would be highly vulnerable.
Highly unusual stratospheric ozone loss and UV-B increases have occurred in the Punta Arenas (Chile) area over the past two decades, resulting in the non-photoadapted population being repeatedly exposed to an altered solar UV spectrum causing a greater risk of erythema and photocarcinogenesis. According to Abarca and Cassiccia (2002), the rate of non-melanoma skin cancer, 81% of the total, has increased from 5.43 to 7.94 per 100,000 (46%).
Human migration resulting from drought, environmental degradation and economic reasons may spread disease in unexpected ways, and new breeding sites for vectors may arise due to increasing poverty in urban areas and deforestation and environmental degradation in rural areas (Sims and Reid, 2006).
Recent studies warn of the possible re-emergence of Chagas’ disease in Venezuela (Feliciangeli et al., 2003; Ramírez et al., 2005) and Argentina (PNC, 2005), and a wider vector distribution in Peru (Cáceres et al., 2002). Some models project a dispersal potential for Chagas’ vector species into new areas (Costa et al., 2002).
A national assessment of Brazilian regions demonstrated that the north-east is the most vulnerable to the health effects of changing climate due to its poor social indicators, the high level of endemic infectious diseases, and the periodic droughts that affect this semi-arid region (Confalonieri et al., 2005).