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Last Edited: 4/30/2008

Public Health Impacts of Climate Change in California: Community Vulnerability Assessments and Adaptation Strategies
Written: July 2007


Climate change is a major cross-cutting public health issue that will significantly increase disease burden in California. Some health impacts will be direct, such as injuries that occur during floods, and others will arise from ecological shifts and environmental degradation, such as emergent infectious diseases or exacerbation of chronic respiratory diseases due to air pollution. In this report, we focus on heat-related illness and mortality.

The public health risks associated with extreme heat events vary across California’s communities, and among the individuals within communities. Vulnerabilities and capacities change over time. To ensure the State’s public health infrastructure has the capacity to withstand the challenges to health posed by climate change and heat, it is essential to know which communities or populations are most vulnerable and then identify strategies and resources to diminish their risk. Advance planning and intervention will be central in order to prevent illness and death.

The primary objective of this community vulnerability assessment, the first in a series, is to identify locations and/or populations with high risk for heat-related illness. To develop a model of community vulnerability we evaluated: (1) past heat waves and published literature to identify risk factors for heat-related illness; (2) a selected set of environmental, health, and demographic “indicators” of risk; and (3) readily available data sources, such as U.S. Census data or other survey data, for demographic risk factors. We used a Geographic Information System (GIS) framework to evaluate patterns of geographic distributions of overlapping indicators.

  • The results of this assessment include the following public health implications of increases in heat related to climate change:California appears to be slowly warming, with temperatures increasing most rapidly in Southern California and in urban centers. Minimum temperatures at night are increasing more rapidly than daytime temperatures, limiting the body’s ability to cool overnight during heat waves. The influence of “heat islands” (geographic areas that are warmer than surrounding areas and form as cities replace natural land cover with pavement, buildings, and other infrastructure) plays a large role in elevated nighttime temperatures. The number and duration of extreme heat events are expected to increase with concomitant increases in heat-related illnesses and deaths.
  • Heat-related illness is a broad spectrum of disease, from mild heat cramps to the most severe – life threatening heat stroke. Virtually all heat-related illness and death is preventable if the appropriate prevention strategies are adopted and implemented by communities and individuals. Specific policies should be implemented at the local level in preparation for heat waves, including establishment and availability of transportation for vulnerable populations to cooling centers, education of social contacts of at-risk populations regarding symptoms of heat illness, and education regarding personal cooling strategies and first aid for heat illness.
  • California counties have varying and unique indicators of risk, including high proportions of elderly, socially isolated populations, children, outdoor workers, the poor, the chronically ill, and the medically under served. County and local health officials are urged to identify vulnerable communities within their jurisdiction. Simple methods can be used such as targeting all ZIP codes where more than 20% of the residents live under the U.S. poverty level, for example. The urban areas of California such as Los Angeles, San Diego, and the San Francisco Bay Area, have the largest absolute numbers of people vulnerable to heat such as children and the elderly. Yet, other areas of the State, which are away from the major urban centers, especially counties with lower socioeconomic status, have high proportions of populations of socially isolated elderly and elderly living in nursing homes.
  • Future heat waves may change geographic risk in California, due to lack of historic physiologic adaptability and capacity to cool. It is recommended that local health officials must focus efforts to prepare areas of the state not historically accustomed to heat. Foothill and mountainous communities throughout the State may be particularly subject to respiratory and heat stress due to lack of historic adaptability, higher ozone levels, higher elevations, and increasing temperatures. Further degradation of air quality due to climate change will amplify occurrence and severity of known air pollution-related adverse health effects.
  • City and land-use planners are advised to work with public health officials to minimize the heat island effect. Increased development of impervious areas in urban locations contribute to the heat island effect. Policies and procedures should be established that require land-use planners and public health officials to work together to minimize the creation of more urban heat islands, and reduce the effects of current ones.
  • Strategic planning and resources are needed to build public health response and surveillance infrastructure, including heat warning systems, and heat-related disease surveillance systems.

Full report in PDF format (Size:  4.3MB)