Health Impacts of Climate Change

Climate change will directly and indirectly impact human health. The direct impacts of climate change depend mainly on exposure to heat or cold waves or extreme weather events. Climate change will extend the area of influence or increase the importance of disease outbreaks that affect the occurrence of indirect health impacts. 
Direct health impacts include injuries and deaths from floods, as well as illnesses and deaths from heat waves. Some infectious diseases are more common in certain areas.
Indirect health impacts include the occurrence of more food- or water-related infections and respiratory diseases because of the anticipated changes in pollen amounts, air pollution concentrations, and environmental damage due to climate change.

The figure below​ shows the linkage between climate change, events that will occur, and impacts on human health. 


​The most immediate threats to public health in Maryland are:

1) Air Q​uality

Climate change affects air quality and exposure to air pollutants in many ways. 
Specific air pollutants that are likely to be increased by climate change and result in negative health impacts include particulate matter, ozone, pollen, and mold.
Increased temperatures, sunlight, and humidity can elevate the levels of ground level ozone formed and the amount of dust particles that remain suspended in the breathable air.
Increased temperatures and carbon dioxide can cause flowers to bloom earlier and elevate the production of common allergens like pollen and mold spores. 

Particulate Matter

Particulate matter comes from cars, trucks, construction equipment, coal-fired power plants, vegetation, open air burning, and livestock. Short-term exposure to particulate matter can lead to acute impairment of lung function.


Ozone is formed in the air by a chemical reaction between volatile organic compounds (VOCs) and nitrogen dioxide when the weather is warm and during the sunny hours of the day. exposure to ozone in the air can make existing health conditions like asthma, chronic obstructive pulmonary disease, and allergies worse, leading to a further decrease in lung function, cause wheezing and asthma attacks and even lead to death. 

Pollen and M​old

Pollen is derived from trees and grass. Molds are forms of fungi that are found naturally in the environment. Climate change is lengthening the growing season for allergenic plants, increasing the amount of pollen produced and the ability for pollen to cause allergic responses. This change may affect people who already suffer from seasonal allergies and may potentially increase the number of people who suffer from allergies. 

These changes in air pollution and allergen production in the air we breathe will cause or worsen respiratory diseases. Some persons, because they are exposed to more pollution, are more affected by poor air quality in the air. Air pollution can penetrate the protective layer of our lungs and cause inflammation, in turn, causing respiratory diseases and symptoms such as coughing and chest pain. Air pollution can impact the cardiovascular system increasing the risk of blood clots and heart attacks. People who already have respiratory diseases such as asthma and chronic obstructive pulmonary disease are even more sensitive to the changes expected from air pollution and allergen production. In addition to people with existing respiratory problems, children, pregnant women, the elderly, the poor, people who are active outdoors and people who spend time in areas with high traffic levels are most likely to be affected. Individuals who work outdoors may be exposed to outdoor air pollutants for long periods of time, and truck drivers can experience long-term exposure to exhaust emissions. Athletes also may be at increased risk because their rapid breathing allows them to take in more air during outdoor activity and therefore more pollutants. 

For more information:
Air Quality Facts, Maryland Department of the Environment 

2) Extre​​me Heat  

As the amount of manmade greenhouse gases increases, a shift in the Earth’s temperature will occur, leading to a dramatic rise in temperatures. This amplification of the “greenhouse effect” will absorb more heat radiated from the Earth’s surface. These changes will increase the surface temperature of the Earth will increase the frequency and intensity of extreme heat events. Also, the built environment is a contributor to the occurrence of extreme heating. The built environment contributes to the formation of “heat islands”. Heat islands are geographic areas that are warmer than surrounding areas. This phenomenon occurs in cities where there are vast areas of concrete and metal that replace natural land covers of vegetation and soil. During heat waves, as nighttime temperatures increase, our bodies do  not have the opportunity to cool off, which increases our risk of experiencing a heat-related sickness.  

Extreme heat will affect impact the health of people who suffer from health conditions that affects the body’s ability to maintain a good temperature balance. 

The populations that will be most impacted are children, the elderly, socially isolated people, those with existing health problems, people living in poor urban areas, people that are active outdoors. 
For more information:

3) Floo​​ds, Droughts, and Extreme Weather Events

Climate change is expected to increase both droughts and flooding. Droughts can occur during prolonged periods of extreme heat and cause soils to harden. The occurrence of heavy downpours has increased and is expected to continue increasing as temperatures rise. Floods can occur after periods of soil dryness, caused by drought and earlier snowmelt due to rising temperatures. 

Extreme weather can impact health in a variety of ways, including:  
  • creating conditions that promote the spread of vector-borne diseases
  • increasing the occurrence of food-borne illnesses, malnourishment and food insecurity
  • causing conditions that can result in the contamination of drinking water.  
The populations that will be most affected by floods, droughts, and other extreme weather events in Maryland are children, the elderly, immunocompromised. 

4) Vector-bor​ne Diseases

Climate is a major factor that may influence disease transmission cycles and disease occurrences. Both a direct and indirect effect on the physical weather conditions such as temperature, rainfall, and humidity can occur because of climate change. 

Dire​​ct effect

​​​Ch​​anges in temp​erature, humidity, rainfall can alter where vectors (vectors are also known as carriers, i.e. mosquito and ticks) multiply and the life-cycles of the germ they transmit.

Indirect effect

​​Climat​​e change can alter biologic​al factors such as the timing and type of plants that grow, the animals that migrate to and from an area, and human behavior. 

​​​These direct (physical) and indire​ct (biological) changes can determine the amount of ticks or mosquitoes that lead to an increase likelihood of human exposure. 

For m​​ore information:
Center for Zoonotic and Vector-borne Diseases, Maryland Department of Health

5) Fo​od-borne Illness

​Climate change will lead to a likely increase in the spread of several foodborne pathogens because the changes in weather patterns for an area can affect the survival, persistence, habitat range, and transmission of a foodborne pathogen. Drought has been shown to encourage crop pests such as whiteflies and locusts, as well as spread mold that produces cancer causing toxins such aflatoxins.  

The aquatic ecosystems and the safety of fisheries may also be threatened through contamination with metals, chemicals, and harmful algal blooms which are a growing problem the Chesapeake Bay. Climate change will increase the occurrence of harmful algal blooms that negatively affect other organisms or produce toxins harmful to animals. Humans may be affected by harmful algal bloom toxins either through direct exposure or by the consumption of seafood containing the toxins. 

For more information:

6) Malnourishment/F​​ood Insecurity

Changes in temperature and precipitation have an impact on the amount of water that evaporates from soil and plants. Although climate change will cause a moderate increase in precipitation, the increases in temperature from the climate forecast models will lead to decreases in soil moisture. The length of the growing season is also a factor for agriculture in Maryland. The climate forecast models project a decrease in the number of frost days where temperatures are below freezing. On the other hand, there will be increases in the growing season. While an increase in growing season may be a benefit for gardeners, the increased active growth time together with reductions in soil moisture will likely cause some regions of the state to experience increased water demand for crop and landscape irrigation. There is also a concern that climate change will lead to an increase of a variety of blasts, rusts, blights, and rots will further devastate already stressed crops, and thereby exacerbate malnutrition, poverty.

7) Sea Lev​el Rise

As our climate changes, sea levels are expected to continue to rise—potentially twice as fast as the one foot increase that occurred during the 20th century. Current projections show that sea levels in Maryland may rise up to two feet by 2050 and as much as four feet by 2100. 

Costal areas my experience: 
  • worsening coastal flooding
  • influencing shoreline erosion
  • submerging tidal wetlands
Maryland’s low-lying Eastern Shore and its barrier and bay islands are the most at risk areas in the state. It is important that communities to begin planning now, in order to reduce future impacts to their existing built environments, as well as to future growth and development. 

For more information:

8) Conta​minated Drinking Water

​In the past, water resource managers and water utilities have relied on predictable variations in climate conditions and water availability. Changes in climate conditions may mean that these previous assumptions are no longer valid. The table below shows the expected impacts of climate change to drinking water: 
​Potential Impacts
​Increased Flooding ​
  • ​Infrastructure damage
  • Increased contamination from waste sites (e.g., animal waste)
  • Increased turbidity – higher treatment levels/costs
  • Increased potential of wells flooding – bacteriological contamination​​
​Increased Air/Water Temperature
  • ​Increased evaporation rates – less water availability
  • Algal blooms – toxins and increased disinfection byproducts
  • Increased raw and finished water temperatures – treatment changes
  • Increased water demand for irrigation and energy production
​Changes in Precipitation and Increased Runoff
  • ​Changes in the seasonality of precipitation – lower stream flow and water availability during peak demand
  • Increased runoff – results in higher pollutant loads in source waters, increased turbidity of surface waters, and stream bed degradation 
​Longer Dry Periods and Droughts
  • ​Decreased surface water and groundwater levels
  • Higher water demand – irrigation, energy, and outdoor water use
​Sea Level Rise
  • ​Low lands will experience inundation and flooding
  • Salt water intrusion in coastal aquifers
  • Low lying wells more vulnerable to flooding
​More Frequent and Intense Tropical Storms
  • ​Damage to utility treatment plants and infrastructure from wind, flooding, and power outages
  • Post-event water quality impacts – higher sediment and pathogen loads
Source: Climate Change Adaptation for Maryland Water Utilities (MDE)

For more information:

At-Ri​​sk Populations

Populations most likely to experience adverse health outcomes from climate change events include, but are not limited to: 
  • Young children
  • Elderly 65 years old and older
  • Elderly people that live alone
  • Communities already stressed by environmental justice and health factors
  • Socially isolated persons
  • Chronically ill people or people with respiratory diseases
  • Persons living in low-lying land areas
  • Persons that have a low socioeconomic status 

Ways to Protect You​rself

There are resources available to help you protect yourself and your family from harmful events that may be associated with climate change, such as days where air pollution levels are elevated or extreme weather events are forecasted. 

Air Protection

​Check news reports on the radio, TV, or internet for pollen reports or daily air quality conditions. You can also visit the  Maryland Department of the Environment’s Air Quality Forecast webpage for air quality information. Limit or avoid outdoor activities on bad air days, particularly if you have asthma or other respiratory conditions.

​For pollen counts visit the National Allergy Bureau webpage. After spending time outdoors, you should wash off pollen that may have collected on your face, skin, or hair.

Extreme Heat

​For protection from extreme heat, limit exertion during heat waves and high temperature days. Hydrate by drinking water frequently, take cool showers or baths, and remain indoors or in shaded areas.

Check on elderly or at-risk friends and neighbors regularly.

Use air conditioning. If your home does not have air conditioning, use fans where possible, keep windows shaded and stay on the lowest level of your home. Because heat rises, upper floors may be hotter than lower levels. 

Visit a place that is air conditioned, such as a movie theater, mall, or the home of a friend or relative who has air conditioning.

Avoid cooking in your home. Instead, eat cold or prepared foods. Using a stove causes a house to heat dramatically.

​Wear loose-fitting, light-colored clothing and wide-brimmed hat. Apply sunscreen with an SPF of 15 or higher 20 minutes before going out into the sun.

Severe Weather

​In the case of a catastrophic extreme weather event, stay informed. Subscribe to local emergency alerts and watch for updates. Have a battery-powered radio or other device available in the event power is lost. 

Check on relatives, friends, and neighbors. 

Have an evacuation plan  and keep emergency supplies on hand.

For more information:
Maryland Emergency Management Agency​

For inquiries email:​