asthma, bronchitis, heart attack, and other cardiopulmonary problems. high ozone concentrations irritate the lungs and thus affect respiratory function, especially among people with asthma. people who are most at risk from breathing in ozone air pollution are those with respiratory issues, children, older adults and those who typically spend long periods of time outside such as construction workers. carbon dioxide levels and human cognition higher levels of indoor and outdoor co2 levels may impair human cognition. pollen allergies depiction of a person suffering from allergic rhinitis a warming climate can lead to increases of pollen season lengths and concentrations in some regions of the world. for example, in northern mid-latitudes regions, the spring pollen season is now starting earlier.: 1049 this can affect people with pollen allergies (hay fever). the rise in pollen also comes from rising co2 concentrations in the atmosphere and resulting co2 fertilisation effects.: 1096 violence and conflicts climate change may increase the risk of violent conflict, which can lead to injuries, such as battle injuries, and death. conflict can result from the increased propensity towards violence after people become more irritable due to excessive heat. there can also be follow-on effects on health from resource scarcity or human migrations that climate change can cause or aggravate in already conflict prone areas. however, the observed contribution of climate change to conflict risk is small in comparison with cultural, socioeconomic, and political causes. there is some evidence that rural-to-urban migration within countries worsens the conflict risk in violence prone regions. but there is no evidence that migration between countries would increase the risk of violence.: 1008, 1128 accidents researchers found that there is a strong correlation between higher winter temperatures and drowning accidents in large lakes, because the ice gets thinner and weaker. available evidence on the effect of climate change on the epidemiology of snakebite is limited but it is expected that there will be a geographic shift in risk of snakebite: northwards in north america and southwards in south america and in mozambique, and increase in incidence of bite in sri lanka. health risks from food and water insecurity climate change affects many aspects of food security through "multiple and interconnected pathways".: 1619 many of these are related to the effects of climate change on agriculture, for example failed crops due to more extreme weather events. this comes on top of other coexisting crises that reduce food security in many regions. less food security means more undernutrition with all its associated health problems. food insecurity is increasing at the global level (some of the underlying causes are related to climate change, others are not) and about 720–811 million people suffered from hunger in 2020.: 1629 the number of deaths resulting from climate change-induced changes to food availability are difficult to estimate. the 2022 ipcc sixth assessment report does not quantify this number in its chapter on food security. a modelling study from 2016 found "a climate change–associated net increase of 529,000 adult deaths worldwide from expected reductions in food availability (particularly fruit and vegetables) by 2050, as compared with a reference scenario without climate change." reduced nutritional value of crops this section is an excerpt from effects of climate change on agriculture § reduced nutritional value of crops. changes in atmospheric carbon dioxide may reduce the nutritional quality of some crops, with for instance wheat having less protein and less of some minerals.: 439 the nutritional quality of c3 plants (e.g. wheat, oats, rice) is especially at risks: lower levels of protein as well as minerals (for example zinc and iron) are expected.: 1379 food crops could see a reduction of protein, iron and zinc content in common food crops of 3 to 17%. this is the projected result of food grown under the expected atmospheric carbon-dioxide levels of 2050. using data from the un food and agriculture organization as well as other public sources, the authors analyzed 225 different staple foods, such as wheat, rice, maize, vegetables, roots and fruits. food production from the oceans a headline finding in 2021 regarding marine food security stated that: "in 2018–20, nearly 70% of countries showed increases in average sea surface temperature in their territorial waters compared within 2003–05, reflecting an increasing threat to their marine food productivity and marine food security".: 14 water insecurity further information: water security § climate change aggregated global water security index, calculated using the aggregation of water availability, accessibility, safety and quality, and management indices. the value ‘0–1’ (with the continuous color ‘red to blue’) represents ‘low to high’ security. aggregated global water security index, calculated using the aggregation of water availability, accessibility, safety and quality, and management indices. the value ‘0–1’ (with the continuous color ‘red to blue’) represents ‘low to high’ security. access to clean drinking water and sanitation is important for healthy living and well-being. this section is an excerpt from effects of climate change § water security. water resources can be affected by climate change in various ways. the total amount of freshwater available can change, for instance due to dry spells or droughts. heavy rainfall and flooding can have an impact on water quality: pollutants can be transported into water bodies by the increased surface runoff. in coastal regions, more salt may find its way into water resources due to higher sea levels and more intense storms. higher temperatures also directly degrade water quality: warm water contains less oxygen. changes in the water cycle threaten existing and future water infrastructure. it will be harder to plan investments for water infrastructure as there are significant uncertainties about future variability of the water cycle. potential health benefits health co-benefits from mitigation the health benefits (also called "co-benefits") from climate change mitigation measures are significant: potential measures can not only mitigate future health impacts from climate change but also improve health directly. climate change mitigation is interconnected with various co-benefits (such as reduced air pollution and associated health benefits) and how it is carried out (in terms of e.g. policymaking) could also determine its impacts on living standards (whether and how inequality and poverty are reduced). there are many health co-benefits associated with climate action. these include those of cleaner air, healthier diets (e.g. less red meat), more active lifestyles, and increased exposure to green urban spaces.: 26 access to urban green spaces provides benefits to mental health as well.: 18 compared with the current pathways scenario (with regards to greenhouse gas emissions and mitigation efforts), the "sustainable pathways scenario" will likely result in an annual reduction of 1.18 million air pollution-related deaths, 5.86 million diet-related deaths, and 1.15 million deaths due to physical inactivity, across the nine countries, by 2040. these benefits were attributable to the mitigation of direct greenhouse gas emissions and the commensurate actions that reduce exposure to harmful pollutants, as well as improved diets and safe physical activity. air pollution generated by fossil fuel combustion is both a major driver of global warming and the cause of a large number of annual deaths with some estimates as high as 8.7 million excess deaths during 2018. placing health as a key focus of the nationally determined contributions could present an opportunity to increase ambition and realize health co-benefits. potential health benefits from global warming it is possible that a potential health benefit from global warming could result from fewer cold days in winter:: 1099 this could lead to some mental health benefits. however, the evidence on this correlation is regarded as inconsistent in 2022.: 1099 global estimates simplified conceptual causal loop diagram of cascading global climate failure, related to the concept of one health estimating deaths (mortality) or dalys (morbidity) from the effects of climate change at the global level is very difficult. a 2014 study by the world health organization tried to do this and estimated the effect of climate change on human health, but not all of the effects of climate change were included in their estimates. for example, the effects of more frequent and extreme storms were excluded. they did assess deaths from heat exposure in elderly people, increases in diarrhea, malaria, dengue, coastal flooding, and childhood undernutrition. the authors estimated that climate change was projected to cause an additional 250,000 deaths per year between 2030 and 2050 but also stated that "these numbers do not represent a prediction of the overall impacts of climate change on health, since we could not quantify several important causal pathways". climate change was responsible for 3% of diarrhoea, 3% of malaria, and 3.8% of dengue fever deaths worldwide in 2004. total attributable mortality was about 0.2% of deaths in 2004; of these, 85% were child deaths. the effects of more frequent and extreme storms were excluded from this study. the health impacts of climate change are expected to rise in line with projected ongoing global warming for different climate change scenarios. society and culture climate justice and climate migrants much of the health burden associated with climate change falls on vulnerable people (e.g. indigenous peoples and economically disadvantaged communities). as a result, people of disadvantaged sociodemographic groups experience unequal risks. often these people will have made a disproportionately low contribution toward man-made global warming, thus leading to concerns over climate justice. climate change has diverse impacts on migration activities, and can lead to decreases or increases in the number of people who migrate.: 1079 migration activities can have impacts on health and well-being, in particular for mental health. migration in the context of climate change can be grouped into four types: adaptive migration (see also climate change adaptation), involuntary migration, organised relocation of populations, and immobility (which is when people are unable or unwilling to move even though it is recommended).: 1079 communication strategies studies have found that when communicating climate change with the public, it can help encourage engagement if it is framed as a health concern, rather than as an environmental issue. this is especially the case when comparing a health related framing to one that emphasised environmental doom, as was common in the media at least up until 2017. communicating the co-benefits to health helps underpin greenhouse gas reduction strategies. safeguarding health—particularly of the most vulnerable—is a frontline local climate change adaptation goal. policy responses due to its significant impact on human health, climate change has become a major concern for public health policy. the united states environmental protection agency had issued a 100-page report on global warming and human health back in 1989. by the early years of the 21st century, climate change was increasingly addressed as a public health concern at a global level, for example in 2006 at nairobi by un secretary general kofi annan. since 2018, factors such as the 2018 heat wave, the greta effect and the october 2018 ippc 1.5 °c report further increased the urgency for responding to climate change as a global health issue. the world bank has suggested a framework that can strengthen health systems to make them more resilient and climate-sensitive.