for Prevention

Climate Change and Health in LA County: Opportunities for Clinical Intervention

Kirsten Lew

Elizabeth Rhoades, PhD

November-December 2017

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As the impacts of climate change continue to intensify across Los Angeles County, clinicians can expect an exacerbation of many patient health problems ranging from respiratory illness to infectious diseases. Residents of LA County are especially vulnerable to health risks associated with increasing extreme heat events, declining air quality, longer and more intense wildfire seasons, expanding habitats of vectors, and conditions that increase risk of water and food-borne disease.1 One acute example of the burden climate change places on regional health is the 2006 record-breaking heat wave which resulted in over 650 excess deaths across California.2 Certain populations within LA County, such as low-income communities, are particularly at risk and may require additional care and resources to protect their health.

This article will summarize the latest science on health risks associated with different aspects of climate change, describe the populations in LA County most likely to be impacted, and offer specific strategies that clinicians can use to protect the health of their patients from the impacts of climate change. The majority of recommendations included in this article were selected from the Public Health Institute’s A Physician’s Guide to Climate Change, Health, and Equity as they address the health impacts of climate change that are projected to be most harmful for LA County residents.


Climate Science

Nearly all scientists and physicians agree that climate change is happening.3 Average global surface temperatures have risen almost 2°F since the late 1800s and 16 of the 17 warmest years on record have occurred this century.4 This rise in temperature is well beyond the range of natural variability and is due to the increasing concentration of greenhouse gases (GHG) that trap heat in the atmosphere. The immediate effects of this process include warming of earth’s surface and oceans, changes in the global hydrologic cycle, receding glaciers and snowpack, sea level rise, and ocean acidification.

The local impacts of climate change depend upon complex climatic processes. As it pertains to health, the most critical downstream impacts of climate change in LA County are projected to be increases in extreme heat, declining air quality, longer and more intense wildfire seasons, expanding habitats of vectors, and favorable conditions for water and food-borne disease.


Map showing how our health is harmed by climate change

Source: Medical Society Consortium on Climate & Health—Medical Alert! Climate Change is Harming Our Health


Key Messages

  • Climate change has direct effects on human health.
  • Some individuals are more vulnerable to the health risks associated with climate change.
  • There are many actions clinicians can take to protect the health of their patients from the impacts of climate change.



Extreme Heat

Extreme heat poses a greater threat to human health in the United States than floods, storms, and lightning combined.5 Extreme heat increases cases of heat-related illness and death, and exacerbates chronic illnesses. Residents in the Los Angeles area are especially at risk of heat-related illness, as the region is expected to warm 4°F by mid-century and the number of heat days (when temperatures are over 95°F) are expected to triple in coastal areas and central Los Angeles and nearly quadruple in the San Fernando and San Gabriel Valleys.6


Current and projected temperature extremes for Los Angeles

Source: UCLA IoES Center for Climate Science


Average August Temperature under Current Climate Change Trajectory in Southern California,
1981-2000 and 2041-2060

Heat map So Cal

Source: UCLA IoES Center for Climate Science


Who is Most Impacted

  • Low-income communities and communities of color often suffer from greater environmental risks of high temperatures due to a lack of trees and green space.
  • Low-income households may also lack access to air conditioning or the ability to transport themselves to public cooling centers.
  • Outdoor workers and athletes are more exposed during extreme heat events.
  • Children, elderly, and those taking certain medications are less able to regulate their body temperature.
  • Patients with chronic conditions such as obesity, diabetes, and renal, respiratory and cardiovascular diseases are at greater risk of complications due to extreme heat. For example, heat stress and associated dehydration can exacerbate existing renal disease and may be linked to new epidemics of chronic kidney disease among individuals without other traditional risk factors.

What Clinicians Can Do

Research shows that many who are especially vulnerable to extreme heat are unaware of their risk. Clinicians are in a unique position to educate patients who are at higher risk about the dangers of extreme heat and how to protect themselves.

  • Recommend strategies for staying cool during extreme heat events such as using air conditioners, going to cooling centers and other places with air conditioning, limiting outdoor activities, and using cool water for showers or baths (see DPH Stay Healthy in the Heat brochure).
    • Cooling centers are official buildings such as libraries, senior centers, and community centers that are open for extended hours during heat waves; a full list can be found here.
  • Advise on the importance of adequate hydration.
  • Inform patients about the risks of some medications and heat.
    • Certain medications increase the risk of heat illness7 (e.g. psychotropic medications, diuretics, antihistamines, benzodiazepines, and some medications for Parkinson’s disease).
    • Medications, including insulin, may lose their effectiveness if subject to very high temperatures. Patients can check package inserts about how high temperatures affect their medicine.  Patients can be advised to not keep medicines in direct sunlight or in a hot car.
  • Encourage healthy patients to check in on vulnerable family, friends, and neighbors during extreme heat events, and help vulnerable patients to access the resources they need to prepare for and cope with extreme heat.


Air Quality

Rising temperatures lead to declines in air quality, as the production of ground-level ozone (a component of smog) increases and heat combines with drought to increase the frequency and severity of wildfires. While the Los Angeles basin has seen improvements in air quality over the last few decades, the Los Angeles-Long Beach area still ranks in the top 10 most polluted cities across all three air quality metrics (ozone, year-round particle pollution, and short-term particle pollution) in the 2017 State of the Air report produced by the American Lung Association.8

Who is Most Impacted

  • Low-income communities and communities of color often suffer from greater environmental risks of poor air pollution due to their vicinity to freeways and industrial polluters and lack of trees and green space.
  • Children are more vulnerable to the respiratory impacts of air pollutants such as smoke.
  • Pregnant women are more sensitive to air pollutants, and exposure can produce adverse pregnancy outcomes.
  • Patients with respiratory disease (e.g. asthma or bronchitis) and cardiovascular disease are at greater risk of exacerbation and complication of their condition by air pollutants.

What Clinicians Can Do

  • Talk to patients about the health risks associated with poor air quality and the conditions which might elevate their individual risk.
  • Advise patients with respiratory conditions to check the Air Quality Index in newspapers or online and limit outdoor activity when air quality is poor.



Wildfires create immediate risks of injury, mortality, and displacement, and further deteriorate air quality. With an already hot and dry climate, LA County can expect more numerous and larger wildfires as a result of climate change. Research indicates that Southern California will experience between 64% - 77% more area burned by wildfires by the middle of this century.9

Wildfire graph

Source: UCLA IoES Center for Climate Science

Who is Most Impacted

  • Low-income families and individuals have greater difficulty bearing the economic burden of displacement or destruction of their homes.
  • Firefighters and other first responders are at greater risk of mortality, injury, respiratory illness, and mental trauma.
  • Children are more vulnerable to the respiratory impacts of air pollutants.
  • Pregnant women are more sensitive to air pollutants and exposure can produce adverse pregnancy outcomes.
  • Patients with respiratory disease, such as asthma or bronchitis, and cardiovascular disease are at greater risk of complications due to air pollutants.

What Clinicians Can Do

Clinicians can talk to their patients about the health risks associated with wildfires and the conditions which might elevate their individual risk.

  • Encourage patients living near fire-prone areas to develop emergency response plans that include keeping written copies of prescriptions and all necessary medications and medical supplies with them in case of an evacuation.
  • Advise patients with respiratory conditions to check the Air Quality Index in newspapers and online and limit outdoor activity during wildfires when air quality is poor. If patients are sheltering in place due to wildfire, advise them to keep windows and doors closed, set air conditioners to recirculate (close air intake), and use HEPA air filters if available to decrease indoor air pollution.


Infectious Diseases

Coccidioidomycosis or “Valley Fever”

Increasing temperatures due to climate change contribute to a drying landscape and potentially higher dust levels. These conditions may increase the risk for Valley Fever, a fungal lung infection that can have serious consequences. LA County has seen a steady increase in Valley Fever cases since 2009 with a 37% increase in cases between 2015 and 2016. More information regarding the increase, endemic areas, and clinical recommendations are in the recent Rx for Prevention article “Increased Coccidioidomycosis (‘Valley Fever’) in Los Angeles County”.10

Who is Most Impacted

  • People who are immunocompromised, pregnant women, people with diabetes, the elderly, as well as African-Americans and persons of Filipino ethnicity are among those at higher risk for developing severe forms of the illness.  
  • Those with occupational exposures that involve disrupting soil in endemic areas including, wildland firefighters, construction workers, archaeologists, military personnel, and workers in mining, gas, and oil extraction jobs.

What Clinicians Can Do

There are no clearly effective interventions to prevent coccidioidomycosis for persons living or working in endemic areas. Clinicians can educate patients about reducing their risk of exposure.

  • Recommend strategies to reduce the risk of breathing fungal spores including, staying inside with windows and doors closed when it is dusty outside; keeping car windows closed and using recirculating air conditioning while driving; and wearing an N95 mask if exposure to a high volume of dust cannot be avoided. Educational resources are available.
  • Educate patients with occupational risks about specific resources for the prevention of work-related Valley Fever.

Vector-borne Diseases

As climate change expands the habitats of vectors, infectious diseases carried by mosquitoes, ticks, and fleas may spread into LA County. The spread of vector-borne diseases is unpredictable, as vector-borne disease incidence depends on many variables, including changing land use, human behavior, demographics, and other factors. However, what is known is that climatic conditions such as temperature, rainfall, and humidity all affect the population size and geographic distribution of vectors, and that changes to these conditions will correspondingly change the range of vector-borne diseases.

One important vector in the context of climate change in LA County is the mosquito. West Nile virus (WNV) cases are increasing in LA County.11 It has been shown that higher temperatures correlate with the increased incidence of West Nile virus in humans.12 In addition, the invasive Aedes mosquitoes (Aedes aegypti and Aedes albopictus) responsible for the transmission of dengue, Zika, and chikungunya, have now been found in Southern California. Although there have been no known locally acquired human infections with any of these three diseases in California to date, the possibility of local transmission is a concern as infected travelers arrive from areas where these diseases are endemic.13

Who is Most Impacted

  • Patients who are active outdoors and outdoor workers are more exposed to vectors.
  • Pets owners may be at increased risk as pets can be carriers of vectors.
  • Pregnant women exposed to some infectious diseases, such as Zika, are at risk for adverse pregnancy outcomes.
  • Older adults and patients with chronic illnesses are at higher risk of experiencing complications from vector-borne diseases.

What Clinicians Can Do to Prevent Mosquito-borne Diseases

  • Educate patients about mosquito-borne diseases (for information, see the Greater Los Angeles County Vector Control District’s Mosquito-borne Disease Threats in Los Angeles County).
  • Provide strategies for preventing bites, such as using insect repellent or covering exposed skin, installing door, and window screens.
  • Encourage all patients to “tip and toss” to reduce mosquito breeding sites around their residences. Use materials and reinforce messages to eliminate standing water and get rid of containers where mosquito eggs may be laid.


Food and Water-borne Disease

Overall warming temperatures and increases in the frequency and severity of floods and drought may increase the risk of food and water-borne disease. Projected warming temperatures in LA County can increase the replication cycle of food-borne pathogens such as salmonella, campylobacter, and E.coli. Flooding produces storm water runoff and overburdens sewage systems, which can introduce pathogens to both water and food sources. Finally, drought conditions can expose individuals to water-borne disease when lower water levels increase the concentration of pollutants and water conservation measures prompt some to limit basic hygiene practices such as handwashing.

Who is Most Impacted

  • Communities with aging water and sewage systems are more exposed to water-borne disease following extreme precipitation and floods.
  • Rural communities that acquire drinking water from small water systems are more exposed to water-borne disease during droughts, as declining water supplies increase the concentration of contaminants.

What Clinicians Can Do

  • Educate patients about food safety during hot weather.
  • Encourage critical hygiene practices during drought.
  • Advise of possible contamination of well water following floods and recommend that patients who acquire drinking water from wells test their well water regularly, as pollutants become more concentrated as water levels decline.



Clinicians can play a critical role in reducing their patients’ health risks associated with climate change. By alerting patients to their unique vulnerabilities and providing strategies to address individuals’ risks, clinicians can prevent negative health outcomes created and exacerbated by climate change.

Health care providers also play a vital role in mitigating or slowing the course of climate change.  In a future article, we will focus on steps health care providers can take on personal, organizational, and policy levels to take action on climate change. Visit the Physician Action Guide to see steps you can take now.

The LA County Department of Public Health Climate Change and Sustainability Program is committed to reducing the public health impacts of climate change in LA County through a variety of strategies, including promoting policies that reduce greenhouse gas emissions, providing guidance on climate resilience, and through outreach and education. Providers are encouraged to visit the program webpage to learn more about our efforts and for resources including presentations and reports.


Additional Resources



  1. Rudolph, L & Harrison, C. A physician’s guide to climate change, health and equity. 2016.  Accessed July 24, 2017.
  2. California Climate Action Team, Heat Adaptation Workgroup. Preparing California for extreme heat: guidance and recommendations, October 2013.  Accessed July 25, 2017.
  3. Sarfaty M, Mitchell M, Bloodhart B, Berg C, Maibach E. Key findings of a National Medical Association physician survey, June 25, 2014. Accessed July 24, 2017.
  4. NASA. Global climate change: facts. Accessed July 25, 2017.
  5. Berko J, Ingram D, Saha S, Parker, J. Deaths attributable to heat, cold, and other weather events in the Unites States, 2006-2010. National Health Statistics Reports. 2014;76: np.
  6. Hall A, Sun F, Walton D, et. Al. Mid-century warming in the Los Angeles region. Accessed July 30, 2017.
  7. Becker J, Stewart L. Heat-Related Illness. Am Fam Physician. 2011 Jun 1;83(11):1325-1330.
  8. American Lung Association. State of the air 2017: most polluted cities. Accessed July 25, 2017.
  9. Jin Y, Goulden, ML, Faivre, N, Ververbeke S, Sun F, Hall A, Hand MS, Hook S, & Randerson JT. Identification of two distinct fire regimes in Southern California: implications for economic impact and future change. 2015. Environmental Research Letters, 10.
  10. Schwartz B, Terashita D. Increased Coccidioidomycosis (“Valley Fever”) in Los Angeles County, Rx for Prevention, 2017 July-August 2017; 7(2) Accessed November 6, 2017.
  11. Los Angeles County Department of Public Health. West Nile Virus and Other Arboviral Diseases: 2017. Los Angeles County Epidemiology Report #14, November 2, 2017. Accessed November 7, 2017.
  12. Hahn MB, Monaghan AJ, Hayden MH, Eisen RJ, Delorey MJ, Lindsey NP, Nasci RS, & Fischer M. Meteorological Conditions Associated with Increased Incidence of West Nile Virus Disease in the United States, 2004–2012. 2015. Am J Trop Med Hyg, 92(5). Accessed November 1, 2017.
  13. California Department of Public Health. Guidance for Surveillance of and Response to Invasive Aedes Mosquitoes and Dengue, Chikungunya, and Zika in California. February 2017. Accessed November 7, 2017.

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Author Information:

Kirsten Lew
CivicSpark Fellow

Elizabeth Rhoades, PhD

Climate Change and Sustainability Program,
Environmental Health Division

County of Los Angeles
Department of Public Health

Rx for Prevention, 2017
November-December 2017;7(4).

Published: November 9, 2017