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Health Effects of Climate Change

Chapter 473 | Disorders Associated with Environmental Exposures · Parts 15-16 – Genetics, Genomics & Precision Medicine · Chapter 473

Key Clinical Points

  1. Climate change is a health emergency impacting human health, medical practice, and the stability of healthcare systems.
  2. Air pollution (PM2.5, ozone, sulfur dioxide, nitrogen dioxide) is a major driver of cardiovascular and respiratory diseases; short-term exposure to PM2.5 increases acute CV risk by 1-3%, while long-term exposure increases it by ~10%.
  3. LMICs bear a disproportionate burden of climate-related impacts, with an estimated 250,000 additional deaths from undernutrition, malaria, diarrhea, and heat stress between 2030-2050.
  4. Air pollution causes approximately 7 million premature deaths annually; coal-burning power plants are associated with double the mortality risk compared to other PM2.5 sources.
  5. Heat-related illnesses (cramps, exhaustion, heatstroke) are increasing in incidence due to rising temperatures and the urban heat island effect.
  6. Plant-based diets may reduce diet-related greenhouse gases by 29-70% by 2050 compared with reference diets.
  7. Pregnancy outcomes (preterm birth, low birth weight, stillbirth) are significantly impacted by PM2.5, ozone, and extreme heat through mechanisms like systemic inflammation and placental injury.
  8. Mesoamerican nephropathy is a specific form of CKD in agricultural workers caused by the synergy of heat exposure (dehydration/hyperthermia) and agrochemical/heavy metal toxicity.
  9. Medication integrity is compromised by extreme heat, specifically for epinephrine injections, naloxone, insulin, and albuterol inhalers.
  10. Climate change impacts are multi-vector, affecting water/food safety, vector ecology, and respiratory health.

DEFINITION & OVERVIEW

• Definition (Harrison's 22e): Climate change refers to the effects of accumulated greenhouse gases (GHGs) in the atmosphere on long-term weather patterns. • Drivers: Anthropogenic emissions (fossil fuel burning, land conversion) → increased mean global temperatures by approximately 1.1°C above preindustrial levels. • Consequences: ◦ Increased frequency of extreme weather (heatwaves, wildfires, droughts, floods) ◦ Resource scarcity (drinking water, food) ◦ Environmental degradation and pollution ◦ Conflict and migration • Clinical Status: Recognized as a health emergency affecting human health, medical practice, and healthcare system stability. • Mitigation Potential: Plant-based diets may reduce diet-related GHGs by 29-70% by 2050 compared with reference diets.

EPIDEMIOLOGY

• Air Pollution Impact: ◦ 7 million premature deaths annually from ambient/indoor air pollution. ◦ Coal-burning power plants → double the mortality risk compared to other PM2.5 sources. ◦ Risk factors: Respiratory (asthma, rhinosinusitis, COPD, lung cancer) and Cardiovascular (MI, stroke, heart failure, hypertension, arrhythmias, VTE). • Climate Projections: ◦ 250,000 additional deaths (2030-2050) from undernutrition, malaria, diarrhea, and heat stress. ◦ Impact disproportionately affects LMICs due to weakened infrastructure. • Displacement: ◦ 108.4 million people (1.4% of humanity) forcibly displaced as of 2022. ◦ Over half the world's population lives within 60 km of the ocean → risk from rising sea levels to infrastructure and water supplies. • Health Disparities: ◦ Climate change amplifies existing disparities (e.g., in the US, impacts on Black, Indigenous, and Latinx populations). ◦ Failure to meet WHO air pollution guidelines (10 μg/m³) compounds structural racism.

ETIOLOGY & PATHOPHYSIOLOGY

• Cardiovascular Disease: ◦ PM2.5 is a primary risk factor for MI, cerebrovascular disease, heart failure, hypertension, DM, arrhythmias, and VTE. ◦ Short-term exposure → 1-3% increased risk of acute CV events. ◦ Long-term exposure → ~10% increased risk (exacerbation of chronic conditions). ◦ Mechanisms: Oxidative stress, inflammation (NF-κB), endothelial dysfunction, impaired EPC function, eNOS uncoupling, NADPH oxidase, Nitric Oxide, Peroxynitrite, TLR activation, adhesion molecules, platelet activation, thrombosis, and smooth muscle proliferation.

Respiratory Disease Pathophysiology

• Climate Impact: Higher temperatures increase burden of asthma, rhinosinusitis, COPD, and lung cancer. • Ultrafine Particle Mechanisms (PM0.1): ◦ Innate Immunity: TNF-α → Cell barrier damage. ◦ Adaptive Immunity: Activated T-cell. ◦ Oxidative Stress: ROS + Fe^{2+} → MAPK, NF-κB, AP-1 activation. ◦ Resulting conditions: Asthma, COPD, lung cancer, interstitial lung disease, lung fibrosis, acute lung injury.

Renal Disease Pathophysiology

• Mesoamerican Nephropathy: CKD in agricultural workers without standard risk factors (DM, HTN, HIV). • Pathways to Kidney Injury: ◦ Dehydration/Volume Loss → Hyperosmolarity (increased vasopressin and aldose reductase) + Crystalluria (urate) + Proximal tubular uptake of toxins from low renal blood flow. ◦ Hyperthermia → Rhabdomyolysis + Primary organ dysfunction. • Contributing Factors: Toxins (pesticides, heavy metals, silica) and heat-associated injury.

Pregnancy Pathophysiology

• Environmental Exposure: PM2.5, ozone, and heat exposure linked to preterm birth, low birth weight, and stillbirth. • Preterm Birth Mechanism: Hematogenous transport of inhaled PM/chemicals → systemic inflammation. • Low Birth Weight Mechanism: Altered maternal cardiac/pulmonary/renal function + placental inflammation + oxidative stress. • Stillbirth Mechanism: Derangements in oxygen transport, DNA damage, and direct placental injury. • Heat-Specific Impacts: Dehydration → altered thermoregulation, blood viscosity, uterine blood flow, placental-fetal exchange, and hormone release (prostaglandin/oxytocin).

CLINICAL FEATURES

• Heat-Related Illnesses: ◦ Includes heat cramps, exhaustion, and heatstroke. ◦ Urban Heat Island Effect: Driven by historical policies (redlining, racial covenants) → higher local temperatures. • Injury & Trauma: ◦ Higher frequency of intense storms → increased drowning, transportation accidents (due to impaired driving at high temps), and assaults (linked to alcohol/drug use). ◦ Note: These are partially offset by fewer falls among the elderly in warmer years. • Mental Health Impacts: ◦ Displacement leads to anxiety, depression, and PTSD. ◦ High temperatures linked to increased suicide rates and domestic violence. ◦ Risk Factor: Psychoactive drugs can interfere with thermoregulation during heat events. • Medication Integrity: ◦ Extreme heat degrades active ingredients or impairs delivery in: Epinephrine, Naloxone, Insulin, and Albuterol inhalers.

DIFFERENTIAL DIAGNOSIS

• Heat-related illness vs. other causes of dehydration/electrolyte abnormalities. • CV events (air pollution) vs. standard causes of MI, stroke, heart failure, HTN, DM, arrhythmias, and VTE. • Adverse pregnancy outcomes vs. other causes of preterm birth, low birth weight, and stillbirth. • CKD in agricultural communities vs. DM, HTN, glomerular disease, or HIV.

DIAGNOSTIC APPROACH

  1. Air Pollution Exposure Assessment:
  2. Monitor ambient/indoor levels → assess PM2.5, ozone, and NO_2.
  3. Respiratory assessment: Pulmonary function tests, chest imaging (asthma, COPD, ILD).
  4. CV assessment: ECG, cardiac enzymes, echocardiography.
  5. Heat-Related Illness Diagnosis:
  6. Clinical assessment of core temperature → hydration status → electrolyte balance.
  7. Pregnancy Exposure Assessment:
  8. Standard obstetric assessment → assess PM2.5, ozone, and heat exposure history.
  9. CKD in Agricultural Communities:
  10. Renal function tests + Urinalysis + Imaging → evaluate for heat/toxin exposure (pesticides, heavy metals).

MANAGEMENT & TREATMENT

  1. Social Ecological Interventions:
  2. Face masks and air purifiers → Wear face masks and install air purifiers in homes.
  3. Reduce in-traffic exposures → Avoid commutes during rush hour.
  4. Reduce in-home penetration of outdoor air pollution → Use indoor air purifiers, close windows, use air conditioners.
  5. Lifestyle changes and preventive medicine → Exercise, healthy diet, screening programs.
  6. Clinical Management Strategies:
  7. Heart Failure: Proactively adjust diuretics (especially diuretic-ACE inhibitor combinations) and increase potassium intake before summer or in heatwave areas → prevent dehydration.
  8. Medication Safety: Ensure proper storage for epinephrine, naloxone, insulin, and albuterol inhalers to prevent degradation/failure.
  9. Continuity of Care: Address risks of displacement interrupting access to medications and clinical care.

PROGNOSIS & COMPLICATIONS

• Respiratory: Increased hospital admissions and premature death from asthma, COPD, and lung cancer due to air pollution. • Cardiovascular: Chronic low-grade inflammation → progression of heart failure and other cardiometabolic diseases. • Renal: Progression to permanent kidney damage (Mesoamerican nephropathy) in agricultural workers. • Pregnancy: Increased incidence of preterm birth, low birth weight, and stillbirth due to environmental stressors.

SPECIAL CONSIDERATIONS

• Pregnancy: High risk for adverse outcomes (preterm birth, low birth weight) from PM2.5, ozone, and heat. • Elderly: Increased risk of heat-related illness; however, some data shows fewer falls in warmer years. • LMICs: Disproportionately affected by undernutrition, malaria, and diarrheal diseases due to climate change.

KEY PEARLS & HIGH-YIELD POINTS

• PM2.5 Impact: Short-term (1-3%) vs. Long-term (~10%) risk for acute CV events. • Mesoamerican Nephropathy: Specific CKD in agricultural workers; caused by heat → dehydration/hyperthermia + toxins (pesticides, heavy metals). • Medication Safety: Albuterol inhalers can explode or degrade in extreme heat; insulin and epinephrine are also compromised. • Proactive Management: Adjust diuretics and potassium for heart failure patients before summer months to mitigate heat-related risks.