national health topics relating to climate change. 1. air pollution ground-level ozone (a key component of smog) is associated with multiple health problems. examples include diminished lung function, increased hospital admissions and emergency room visits for asthma, and increases in premature deaths. health-related costs of the current effects of ozone air pollution exceeding national standards have been estimated at $6.5 billion (in 2008 u.s. dollars) nationwide, based on a u.s. assessment of health impacts from ozone levels during 2000–2002. 2. allergens and pollen climate change will potentially lead to shifts in precipitation patterns, more frost-free days, warmer seasonal air temperatures, and more carbon dioxide (co2) in the atmosphere. these occurrences will lead to both higher pollen concentrations and longer pollen seasons, causing more people to suffer more health effects from pollen and other allergens. in a recent study looking at pollen metrics from 60 metric stations in north america between 1990 and 2018 scientists found that pollen seasons were starting up to 20 days earlier and lasting for up to eight days longer. 3. diseases carried by vectors within the united states the impact of climate change from domestically acquiring diseases is uncertain due to vector-control efforts and lifestyle factors, such as time spent indoors, that reduce human-insect contact. however, the impact on the geographical distribution and incidence of vector-borne diseases in other countries where these diseases are already found can still impact americans, especially due to travel and trade. 4. food and waterborne diarrhea diarrheal diseases are more common when temperatures are higher, although location and pathogen can also affect the pattern. extremely high and low precipitation has also been linked to an increased frequency in the occurrence of diarrheal diseases. additionally, sporadic increases in stream flow rates, often followed by rapid snowmelt and changes in water treatment, have also been linked outbreaks. risks of waterborne illness and beach closures resulting from changes in the magnitude of recent precipitation (within the previous 24 hours) and in lake temperature, are expected to increase in the great lakes region because of climate change. in the united states, those who are exposed to inadequately or untreated groundwater are most likely to be affected. additionally, children and the elderly are most vulnerable to serious outcomes. 5. food security food production, quality, distribution, and prices can all be affected by climate change. not only are crops affected by changes in rainfall and extreme weather, but livestock and fish are also being impacted. the related health effects will vary. due to rising prices, poor persons will turn to “nutrient-poor but calorie-rich foods and/or they endure hunger, with consequences ranging from micronutrient malnutrition to obesity.” additionally, nutritional quality will be impacted because “elevated atmospheric co2 is associated with decreased plant nitrogen concentration, and therefore decreased protein, in many crops, such as barley, sorghum, and soy. the nutrient content of crops is also projected to decline if soil nitrogen levels are suboptimal, with reduced levels of nutrients such as calcium, iron, zinc, vitamins, and sugars. this effect can be alleviated if sufficient nitrogen is supplied.” 6. mental health and stress related disorders extreme weather and high temperatures can affect mental health in a variety of ways for both individuals with, and without preexisting mental health conditions. additionally, the symptoms can be short-term or long lasting. for example, studies done after hurricane katrina hit the united states gulf coast showed that children affected by the hurricane have found high rates of depression, anxiety, behavioral problems and post- traumatic stress disorder (ptsd). 7. precipitation extremes the united states has seen an increase in the frequency of heavy precipitation events, and the upward trend is supposed to continue throughout the different regions of the country. these events such as floods and droughts present immediate risks to the health of americans during the occurrence but can also affect health in the period following the catastrophe. for example, flooding can cause water damage to buildings leading to mold or need for demolition. these events can necessitate the forceful relocation of an entire family which may be distancing them from schools, primary doctors and other resources that they may have gotten used to. 8. temperature extremes increasing concentrations of greenhouse gases lead to an increase of both average and extreme temperatures. this is expected to lead to an increase in deaths and illness from heat and a potential decrease in deaths from cold. days that are hotter than the average seasonal temperature in the summer or colder than the average seasonal temperature in the winter cause increased levels of illness and death by compromising the body’s ability to regulate its temperature or by inducing direct or indirect health complications. loss of internal temperature control can result in a cascade of illnesses, including heat cramps, heat exhaustion, heatstroke, and hyperthermia in the presence of extreme heat, and hypothermia and frostbite in the presence of extreme cold. temperature extremes can also worsen chronic conditions such as cardiovascular disease, respiratory disease, cerebrovascular disease, and diabetes-related conditions. prolonged exposure to high temperatures is associated with increased hospital admissions for cardiovascular, kidney, and respiratory disorders. 9. wildfires in 2021 we have seen an increase in the news and social media coverage about wildfires spreading throughout california as shown in the image at the end of the section. no doubt, one of the many effects of climate change, these wildfires have many harmful (short and long term) effects on the health of americans. not only do many people lose their homes, livelihoods and even lives in these fires, but smoke exposure has many negative effects on physical health as well. it increases respiratory and cardiovascular hospitalizations; emergency department visits; medication dispensations for asthma, bronchitis, chest pain, chronic obstructive pulmonary disease, and respiratory infections; and medical visits for lung illnesses.