The impact of climate change on oral health - A multifaceted perspective

INTRODUCTION

The United Nations Framework Convention on Climate Change (CC) attributes CC to “direct or indirect human activity that alters the composition of the global atmosphere and which is in addition to natural climate variability observed over comparable time periods.”^[1] Over the past decade and beyond, terms such as CC, Global Warming (GW), and Climate Emergency have been used to describe the foremost sustainability challenge of the 21^st century.^[2] Besides extreme weather events, sea level rise, and heightened temperatures, the consequences of CC include shifts in water pH, drought, and forest fires, leading to the emergence or heightened transmission of diseases with various adverse impacts on human health.^[3,4] CC poses a profound threat to human health, impacting not only the physical environment but also every facet of natural and human systems, including social and economic conditions and the effectiveness of health systems. As a “threat multiplier,” it risks undermining and even reversing decades of progress in health.^[5] The health impacts of this global imbalance, both direct and indirect, include heat-related illnesses, the spread of vector- and waterborne diseases, greater exposure to environmental toxins, exacerbation of cardiovascular and respiratory conditions due to deteriorating air quality, and heightened mental health stress, among other effects.^[6]

Health and CC research are a critical component, ensuring that health programs are climate-informed, robust, and up to date. The World Health Organization (WHO) Health and CC Global Survey Report 2021 reported that 74% of countries (70 out of 95) reported inter-ministerial collaboration on health and CC research to address climate-associated health vulnerability and develop sustainable healthcare facilities.^[7] While oral health is a critical component of overall health, the impact of CC on oral health remains understudied. Given the interconnectedness of oral and systemic health, CC can indirectly lead to both short-term and long-term oral health consequences. Assessing the specific effects of CC and related disasters is complex due to their interplay with social, environmental, and biological factors at both individual and systemic levels. To effectively mitigate these impacts, it is essential to identify and address the individual and community-level factors influenced by CC. This knowledge will aid in the development of adaptive oral health policies and reforms.^[8-13]

There is mounting evidence that CC is already adversely affecting human health^[12] [Figure 1]. The oral cavity and the gut are both characterized by dense and diverse microbial communities. While these two anatomical sites are physiologically distinct, they are interconnected and can exert reciprocal influences on each other.^[9] Alterations in the composition and function of the gut microbiota can impact intestinal permeability, digestive processes, metabolic functions, and immune responses inducing a pro-inflammatory state, which is implicated in the pathogenesis of various diseases, including gastrointestinal, metabolic, immunological, and neuropsychiatric disorders.^[10] Recent research indicates that dysbiosis strings a potential link between oral health and systemic diseases, suggesting that the oral-gut axis may play a causal role in this association.^[11] CC affects human health through three pathways.

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Figure 1:

Pathways through which climate change impacts human health.

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Human-induced warming, drought, and flooding increase health risks such as respiratory, cardiovascular, and mental illnesses, with vulnerable populations disproportionately affected due to intensified environmental and socioeconomic stressors.^[14-18] CC intensifies vector-borne, waterborne, and foodborne disease risks, altering transmission dynamics, contaminating resources, and increasing illnesses in humans, livestock, and vulnerable populations globally. All these have a direct bearing on oral health and/or oral healthcare delivery.^[19-21] It also disproportionately impacts marginalized groups, exacerbating food insecurity, mental health vulnerabilities, societal instability, and resource scarcity, with severe consequences for global health and security, which are known to influence outcomes of oral health.^[22-25]

CC presents a substantial threat to oral health, with a complex network of direct, indirect, and distant impacts.^[26]

Effects of climate on oral health:

• Salivary factors

  • pH

  • Flow rate

  • Protein/water/carbohydrate content in food

• Integrity of tissues

  • Hard tissues

  • Mucosa

• Immunological factors

  • Host

  • Microbial factors

• Modification of systemic inflammation^[26,27]

Global environmental changes propagate through social, biological, and ecological systems, creating a feedback loop that intertwines oral and systemic health [Figure 2]. SDG 13, “Climate Action,” emphasizes urgent actions to combat CC and its impacts, including its overlooked effects on oral health. CC directly and indirectly influences oral health through various mechanisms.

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Figure 2:

Feedback loop of the impact of climate change on systemic and oral health through oral dysbiosis.

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Elevated temperatures, humidity, and fluctuations in precipitation patterns can affect water availability and can foster an environment that promotes the growth of oral bacteria, increasing the risk of dental caries.^[28] GW may contribute to a cumulative increase in children’s fluoride exposure. This is due to multiple factors, including elevated fluoride levels in drinking water, toothpaste, supplements, infant formula, and food products derived from animals and crops cultivated in fluoride-rich environments. As climatic conditions influence the permissible fluoride intake threshold, increased exposure could potentially elevate the risk of dental fluorosis and caries.^[29] CC-induced oxidative stress, caused by an imbalance between pro-oxidant and antioxidant factors, may contribute to enamel hypoplasia.^[30] CC increases the risk of early childhood caries through rapid climate-induced alterations in soil composition, nutrient solubility, and plant trace element absorption.^[29] Even minor variations in temperature can significantly impact salivary flow rates. For example, studies have demonstrated decreased unstimulated salivary flow in soldiers during summer months, potentially attributed to increased dehydration during this period. Similarly, a slight temperature increase in a warm climate can influence unstimulated salivary flow. Severe dehydration, exceeding 8% of body fluids, can result in complete cessation of salivary secretion.^[31] Stimulation of cold receptors elicits an increase in salivary flow and exposure to cold air can stimulate the sympathetic nervous system and the hypothalamic-pituitary-adrenal axis, resulting in increased amylase production.^[32]

CC has been linked to a significant increase in asthma rates, primarily due to factors such as prolonged and intense wildfire seasons, extended pollen seasons, elevated air pollution, and increased ground-level ozone. Common asthma medications, including antihistamines and bronchodilators, can cause xerostomia and increased sugar exposure. Individuals with asthma have been shown to have a heightened risk of dental caries, gingival inflammation, and altered salivary pH. Similarly, chronic pulmonary diseases, which are associated with CC-induced air quality degradation, have been strongly linked to periodontal disease.^[27] Release of chlorofluorocarbons (CFCs) and halons has been exacerbated by GW, leading to ozone depletion, elevated temperatures, and air pollution, causing an increased risk of carcinogenesis, oral cancer, and increased annual skin cancer rates.^[28,33] Biological, social, and ecological impacts on the food chain contribute to food and fuel burdens.

CC poses a significant threat to global food and fuel security by disrupting the food supply chain at multiple stages, from production to consumption, food, nutrition insecurity, and disruption of healthcare supplies.^[34,35] The increasing consumption of unhealthy diets, particularly those high in sugar and processed foods, is a major driver. This dietary trend not only impacts oral health but is also linked to a range of systemic health issues, including type 2 diabetes, cardiovascular disease, chronic respiratory diseases, and cancer. The cariogenic nature of sugars, which serve as a substrate for acid-producing oral bacteria, is well established. In addition, the consumption of acidic foods and beverages can erode tooth enamel, leading to dental erosion and hypersensitivity. Saturated fats may promote the growth of bacteria associated with periodontal disease, and alcohol consumption is a significant risk factor for oral cancer. Emerging research suggests that commercial food processing methods, such as extrusion-cooking, can increase the cariogenicity of certain foods.^[36]

Higher consumption of ultra-processed foods and drinks leads to an increased risk of dental caries,particularly in children.^[37] Tooth loss in adults has been associated with dietary patterns characterized by low consumption of fruits, vegetables, vitamin C, and vitamin E, and high consumption of processed foods and fatty acids. A poor diet quality, particularly one high in saturated fat, has been linked to the progression of periodontal disease.^[38] Malnutrition is associated with cancrum oris, characterized by gingivitis and ulcerative periodontal lesions. Malnutrition can also contribute to enamel hypoplasia, dental caries, and delayed tooth eruption.^[27] Biological, social, and ecological impacts, along with food and fuel burdens, contribute to health inequity.

“The climate crisis is a health crisis,” Dr. Maria Neira, WHO’s Director of Environment, CC, and Health, emphasized the urgent need to address the health implications of CC and highlighted the importance of implementing strategies that not only mitigate CC but also promote public health in Conference of the Parties (COP) 29, Baku.^[39] Health inequity represents a compounding factor, exacerbated by the disproportionate effects of CC on marginalized populations. Vulnerable groups often lack resources to mitigate environmental impacts, leading to disparities in healthcare access, hygiene, and nutrition. Such inequities perpetuate poor oral health outcomes.^[40] COP 29 focused on Climate Amplified Disease and Epidemics: Characterization of and Response to Epidemics in the Global South and Nature-Based Solutions for Health: Implementing a One Health Approach between Conservation and Health Organizations.^[39] Biological, social, and ecological impacts lead to food and fuel burdens, driving health inequity and resulting in oral dysbiosis, which amplifies systemic health consequences linked to CC.

Oral dysbiosis serves as a central node linking CC, systemic health, and oral health. CC-induced dietary shifts can increase health risks through dysbiosis.^[41] CC can disrupt the balance of the soil microbiome, which in turn affects the nutritional quality of crops. These altered crops can then negatively impact the human gut microbiome, leading to a less diverse microbial community, decreasing bacteroides, and increasing proteobacteria similar to that seen in malnutrition. An increased bacteroidetes-to-firmicutes ratio, which is often associated with obesity and a decrease in lactic acid bacteria is observed.^[42] Elevated levels of Verrucomicrobia and decreased levels of the phyla cyanobacteria, actinobacteria, and firmicutes have been associated with air pollution.^[43] Temperature is a significant environmental factor influencing the composition of microbial communities across various human body sites, including the skin, gut, and oral cavity.^[44] The WHO predicts that CC-related temperature increases could result in the deaths of over 33,000 children under 15 due to diarrheal diseases by the year 2050.^[45] This imbalance allows pathogenic bacteria to proliferate, suppressing beneficial microorganisms. Consequently, the dysbiotic state further exacerbates mucosal barrier dysfunction, perpetuating a vicious cycle of inflammation and microbial imbalance.^[44] CC interacts with environmental epigenetics, modifying gene expression patterns through microbial metabolites like short-chain fatty acids. These epigenetic alterations also influence immune cell function and the composition of the gut microbiome, which (dysbiosis) significantly impacts the health of humans.^[44,45]

Given the anatomical proximity of the oral cavity to the intestine, a potential bidirectional relationship between alterations in the gut microbiota and changes in the oral microbiome exists. This complex interplay underscores the intricate connection between oral and systemic health. The intricate relationship between oral and gut microbiota is mediated by various pathways. Oral bacteria can reach the gut through swallowing, hematogenous dissemination, or within immune cells. Specific oral pathogens, such as Porphyromonas gingivalis, Fusobacterium nucleatum, and Aggregatibacter actinomycetemcomitans, have been implicated in modulating the gut microbial community.^[46] Disruptions to the oral microbiome have been implicated in the development and progression of various chronic diseases. These include systemic conditions such as endocarditis, osteoporosis, and rheumatoid arthritis, as well as noncommunicable diseases such as obesity, diabetes, cancer, and neuropsychiatric disorders.^[47] Oral dysbiosis is not merely a localized condition but a key contributor to broader systemic health issues.

Oral dysbiosis initiates the bidirectional effects, leading to oral health effects driven by CC. Internal effects include microbial modification, drug resistance, alterered metabolism, dysbiosis and impact on systemic health.

ORAL HEALTH IN THE FACE OF CLIMATE CRISIS: DISPLACEMENT, DISPARITIES, AND DISASTER RESPONSE

Climate refugees (CR) may often experience worse oral health outcomes, such as periodontal diseases and dental caries, radical departure from native food habits, acclimatization issues, access barriers due to language and cultural differences, institutional discrimination, and restricted access to dental health services.^[51] Oral diseases are major health issues that refugees face, including a high burden of periodontal disease and dental caries.^[52] For example, 80% of refugees in Canada had untreated caries or periodontal disease.^[53] Dental caries is the leading reason for tooth extractions among refugees, making it the most frequent dental procedure and contributing to a high number of missing teeth, significantly affecting their quality of life. Preventive dental care is rarely utilized, with a greater focus on urgent, problem-based treatments like extractions. Many refugees reported suffering from tooth pain, and just over half had received only a single session of oral hygiene advice since arriving in the host country.^[51,54,55] Refugees have faced significant difficulties in obtaining dental care in host countries, with major barriers including cost (affordability), ease of reaching services (accessibility), suitability of services to their needs (accommodation), limited service options (availability), lack of information (awareness), and cultural or personal comfort with the care provided (acceptability).^[51]

Pacific populations experience significant unmet oral health needs, ethnic disparities, and barriers preventing care. Barriers to accessing oral healthcare include socioeconomic factors such as the cost of dental care, education levels, income, and the unavailability of health insurance, as well as a lack of trained personnel and health behaviors and beliefs.^[56] Pacific ethnicity has been linked to a higher prevalence of dental caries, with a greater proportion of Pacific children consistently falling into the highest Decayed, Missing, and Filled Teeth (DMFT) category compared to other ethnic groups. This aligns with other findings showing that Pacific children in New Zealand tend to receive fewer restorative treatments and undergo more tooth extractions than their peers from other ethnic backgrounds.^[57,58]

As of the end of 2023, 110 million people worldwide have been forced to flee their homes, including more than 36.4 million refugees.^[59] Oral health often receives insufficient attention within primary healthcare provisions for refugee communities. In refugee camps, there is frequently a lack of dental personnel. Managing transportation costs to health centers and finding childcare to attend medical appointments can also be challenging.^[60,61]

Marginalized and socially excluded groups face disproportionately worse oral health outcomes and poorer access to dental services compared to the general population.^[62] These inequalities are intensified by CC, which exacerbates existing health disparities through multiple pathways. CC contributes to oral diseases such as dental caries, erosion, periodontal disease, and oral infections by affecting environmental conditions and access to care. Extreme weather events disrupt dental service availability and increase oral health risks due to poor hygiene and contaminated water. Furthermore, climate-related food insecurity leads to poor nutrition, which negatively impacts oral health. Stress and mental health challenges induced by CC can also worsen oral hygiene and increase bruxism, further deepening oral health inequalities.^[63] Socioeconomic status strongly influences oral health outcomes. Studies show that individuals with lower education, income, and economic security report significantly poorer oral health. People in the lowest income quintile are over 1.3 times more likely to report poor oral health compared to those in the highest quintile. These disparities are compounded in marginalized communities, where limited resources and systemic barriers restrict access to preventive and curative dental care.^[64]

Indigenous women, especially those pregnant with indigenous children, encounter significant barriers in accessing dental care, which worsens their oral health outcomes. A study of South Australian Indigenous women found low dental service utilization during pregnancy (only 35.7%), despite high perceived need for care and positive oral health beliefs.^[65] Key barriers include difficulty navigating complex dental care systems, low health literacy, language and cultural differences, and limited availability of culturally appropriate services.^[65,66]

Indigenous Australians often rely on Aboriginal community-controlled health services, but these may not always provide dental care, forcing reliance on mainstream services that are harder to access due to systemic and cultural barriers. Innovative approaches such as health navigator programs, indigenous liaison officers, and integration of social media and technology to improve service approachability have shown promise in improving dental care uptake among Indigenous women. Programs like the Midwifery-Initiated Oral Health Dental Service, which facilitates referrals and follow-up for pregnant Indigenous women, have demonstrated effectiveness in increasing dental service utilization and could serve as models for broader implementation.^[65]

Natural disasters such as floods and hurricanes severely disrupt healthcare infrastructure, including dental clinics, making them inaccessible or completely destroyed. This leads to significant interruptions in healthcare delivery and worsens health outcomes for affected populations. Hosokawa et al., reported that older people hesitated to wash their dentures because of an insufficient water supply after the 2011 Great East Japan Earthquake.^[67]

Maintaining oral health is challenging for both rescuers and earthquake survivors living in temporary shelters. The harsh living conditions and psychological stress often lead to oral health problems such as gingivitis, pulpitis, periodontitis, ulcers, and lichen planus. With the regular medical infrastructure and dental clinics severely damaged by the earthquake, dentists relied on portable dental equipment to treat these oral diseases and alleviate patients’ discomfort.^[68]

WORLDVIEWS AND KNOWLEDGE SYSTEMS

Harmony with nature (Amazonian tribes): The Yanomami people in the Amazon rainforest traditionally use plants with antimicrobial properties for oral hygiene. They also avoid polluting water sources to maintain a healthy environment for themselves and future generations.^[69]

Sustainability (Japanese culture): The Japanese philosophy of Mottainai emphasizes not wasting resources. This translates to a focus on preventative dental care, like regular brushing and flossing, to avoid needing complex and resource-intensive dental procedures.^[70]

Traditional medicine (Australian aboriginals): Aboriginal Australians use various native plants for treating oral ailments. CC and habitat loss can threaten the availability of these crucial medicinal plants.^[71]

Hygiene practices (Water Scarcity in Africa): In areas facing water scarcity, like parts of Sub-Saharan Africa, traditional brushing practices might be limited. Here, communities might adopt alternative methods like using miswaks (chewing sticks) for oral hygiene, requiring less water.^[72]

Dietary choices (Inuit communities): CC impacting arctic ecosystems can threaten food security for Inuit communities. Conventionally reliant on fish and marine mammals, a shift toward processed foods due to limited access to fresh options can increase sugar intake and contribute to poor oral health.^[73]

EMERGING THEMES AND GLOBAL INITIATIVES TO DEEPEN THE ANALYSIS OF CC’S IMPACT ON ORAL HEALTH

AI-driven risk prediction: Machine learning models can analyze climate data (e.g., wildfire patterns, air quality) to predict communities at higher risk of oral health issues such as xerostomia, periodontal disease due to pollution, and heat stress. For example, AI tools are already identifying dental caries earlier and mapping vulnerable populations using satellite data.^[74,75]

Remote teledentistry: AI-powered platforms enable remote monitoring of oral health in climate-disaster-prone regions, reducing gaps in care during infrastructure disruptions.^[76]

Holistic interconnectedness: Expand the discussion to include the planetary health model, which links oral health to Earth’s systems (e.g., biodiversity loss, pollution). For instance, deforestation exacerbates air pollution, worsening oral diseases, while sustainable agricultural practices could improve nutrition and reduce caries risks.^[77]

One Health approach: Emphasize collaboration between dental professionals, ecologists, and policymakers to address zoonotic diseases (e.g., Zika) that have oral health implications.^[77]

Universal health coverage (UHC) integration: The UN’s Pact for the Future advocates for oral health inclusion in UHC to combat inequities worsened by climate-driven disasters. This includes funding preventive care and teledentistry in low-income regions.

Workforce adaptation: Training dental teams in climate adaptation strategies, such as using biodegradable materials or managing heat-stressed patients, aligns with the WHO’s Global Oral Health Action Plan.^[78]

Carbon-neutral clinics: Highlight innovations such as eco-friendly dental materials, renewable energy use, and reduced water consumption to lower the healthcare sector’s carbon footprint.

Circular economy in dentistry: Promote recycling of dental waste (e.g., amalgam separators) and digital workflows (e.g., AI-guided 3D printing) to minimize environmental harm.^[27,78]

Stress and oral health: Link extreme weather events to increased bruxism, temporomandibular Joint (TMJ) disorders, and poor oral hygiene due to climate anxiety or displacement.

Dietary shifts: Explore how climate-driven food insecurity leads to reliance on processed foods, worsening caries, and malnutrition-related oral diseases.^[79]

Loss and damage fund: Advocate for climate finance mechanisms (e.g., the COP28 Health Declaration) to fund oral health infrastructure in vulnerable nations.

Green climate fund allocation: Push for grants targeting oral health adaptation, such as fluoridation programs in drought-affected areas.^[76]

Life-course equity: Integrate oral health into lifelong climate adaptation strategies, ensuring care continuity from childhood to old age despite environmental stressors.

Community-led solutions: Empower marginalized groups through participatory programs addressing localized climate risks (e.g., water scarcity in Indigenous communities).^[77-79]

CONCLUSION

Europe experienced record-breaking heatwaves in the summer of 2023, with the total number of days exposed to extreme heat increasing by a staggering 97% in the past decade compared to the previous one. CC significantly impacts oral health, increasing vulnerabilities and introducing challenges like heightened risks of periodontal disease from rising temperatures and air pollution, as well as disrupted dental care due to extreme weather. The dental profession, while contributing to environmental harm through energy use and waste, can lead sustainability efforts by adopting energy-efficient technologies, reusable materials, and tele-dentistry. Educating patients and policymakers on climate-oral health links and integrating sustainability into dental curricula are vital. Through collaboration and eco-friendly practices, dentists can align environmental stewardship with improved health outcomes, fostering a resilient system that addresses health inequities and protects the planet.