Environmental Determinants of Health

Introduction

The environmental determinants of health encompass the physical, natural, built, and macro-environmental factors that influence individual and population health. Understanding these determinants is essential for evaluating health outcomes, health equity, and the effectiveness of interventions.

Applying a Critical Lens to Health Research

Critical Scholarship in Health

Critical scholarship involves questioning accepted knowledge and evaluating the quality and reliability of health research. Scholars should ask:

• How do we know this to be true?

• Are there other ways to understand this?

• Whose knowledge is this?

• How do I judge the quality of the evidence?

Critical appraisal is the systematic assessment of research to determine its trustworthiness, value, and relevance.

Measurement of Health Status

Health status is measured using indicators that allow for comparison across populations and regions. Common indicators include:

• Life Expectancy at Birth: The average number of years a newborn is expected to live if current mortality trends continue.

• Infant Mortality Rate: Number of deaths of infants under 1 year per 1000 live births.

• Under-5 Mortality Rate: Probability that a child will die before age 5, per 1000 live births.

• Maternal Mortality Ratio: Number of women who die due to pregnancy/childbirth complications per 100,000 live births.

• Neonatal Mortality Rate: Deaths of infants under 28 days per 1000 live births.

Vital statistics (births and deaths) are foundational for health data, but their quality varies globally.

Key Health Indicators: Global Comparisons

Life expectancy and under-5 mortality rates vary significantly by region, reflecting disparities in health development.

• Life Expectancy at Birth: Higher in North America and Europe, lower in Sub-Saharan Africa.

• Under-5 Mortality Rate: Highest in Sub-Saharan Africa, lowest in North America.

Methodologies in Health Studies

• Quantitative Research: Collects numerical data (e.g., surveys, vital statistics).

• Qualitative Research: Collects descriptive data (e.g., interviews, focus groups).

Both approaches are valuable for understanding health determinants.

Determinants of Health Framework

Overview of Determinants

Health is influenced by multiple determinants, including:

• Physical Environment: Water, sanitation, air pollution

• Social Environment: Socio-economic status, education, culture, gender norms

• Healthy Behaviours: Coping skills, lifestyle choices

• Employment and Working Conditions

• Access to Health Services

• Healthy Child Development

Dahlgren and Whitehead Model

This model illustrates the layers of health determinants, from individual factors to broader socio-economic, cultural, and environmental conditions.

Environmental Health Burdens

Major Environmental Health Burdens

• Poor sanitation and lack of clean water

• Air pollution (indoor and outdoor)

• Inadequate housing

• Changing land use and climate

• Pollution and exposure to toxics

Environmental factors contribute significantly to the global burden of disease, especially in low- and middle-income countries.

Air Pollution

Types and Sources of Air Pollutants

Air pollution is a critical environmental health determinant, with both indoor and outdoor sources:

• Outdoor: Industrial waste, vehicle emissions, particulate matter (PM10, PM2.5), ozone, nitrogen oxides, sulfur dioxide, carbon monoxide, ammonia, lead, PAHs, VOCs

• Indoor: Solid fuels (biomass, animal dung), cooking and heating fires

Children are especially vulnerable to air pollution, which can cause respiratory and developmental issues.

Health Effects of Indoor Air Pollution

• Miscarriages, early delivery, low birth weight

• Child mortality (up to 10% of under-5 deaths)

• Impaired brain development

Access to Safe Drinking Water

Causes and Consequences of Unsafe Water

• Causes: Pollution, contamination, inadequate sanitation, poor hygiene

• Consequences: Diarrheal illnesses (e.g., gastroenteritis, cholera), vector-borne diseases (e.g., malaria, dengue, schistosomiasis)

Water-Related Infections

• Water-borne: Ingested (e.g., cholera)

• Water-washed: Poor hygiene (e.g., hepatitis A)

• Water-based: Aquatic intermediate host (e.g., schistosomiasis)

• Water-related insect vector: Insects dependent on water (e.g., malaria)

Schistosomiasis is a water-based infection caused by parasitic worms, leading to conditions such as ascites.

Canadian Context: Indigenous Communities

Many rural and remote Indigenous communities in Canada lack access to clean water, resulting in long-term health advisories and increased health risks.

Built Environment

Impact of Housing and Living Spaces

Housing affects health through internal conditions (hazards, pollutants), area characteristics (social benefits, location), and housing tenure (psychological and financial dimensions).

• Pollutants, building materials, mold/bacteria, cleaning products, carbon monoxide, gases, cigarette smoke, solvents, animal dander, fireplaces

Residential Segregation

Residential segregation leads to health disparities, with higher rates of adverse outcomes in highly segregated areas.

Homelessness and Core Housing Need in Canada

Homelessness can be unsheltered or hidden, affecting millions of Canadians. Core housing need includes lack of affordability, suitability, and adequacy.

Macro-Environmental Factors

Disasters, Governance, and Climate Change

Macro-environmental factors include natural disasters, governance structures, war, and climate change. These factors have direct and indirect impacts on health.

• Natural Disasters: Cause ecological disruption, loss of life, and require extraordinary response.

• Complex Humanitarian Emergencies: Characterized by violence, displacement, and societal collapse.

• Climate Change: The greatest health threat, causing rising temperatures, extreme weather, sea level rise, and increased CO2 levels.

Economic and Health Impacts of Disasters

Increasing frequency and severity of disasters raise economic costs and strain health systems.

Governance and Health Outcomes

Democratic governance is associated with higher life expectancy and lower infant and maternal mortality, though exceptions exist due to ecological fallacy.

War and Health

War impacts physical, mental, and emotional health. Security is a basic human need, as illustrated by Maslow's hierarchy.

Summary

Environmental determinants of health are multifaceted and interact across individual, community, and global levels. Key burdens include air pollution, unsafe water, inadequate housing, and climate change. Health outcomes are shaped by governance, social structures, and access to resources. Addressing these determinants requires critical scholarship, effective measurement, and targeted interventions.