Human Risk Assessment: Protecting Health Amid Development

Every time a new factory is built, a highway is expanded, or a mining operation begins, people living nearby face potential health risks. These risks don’t appear out of nowhere – they stem from changes in air quality, water sources, soil conditions, and workplace environments. Human risk assessment is the systematic process used to identify, evaluate, and manage these health threats before they cause serious harm. It is a cornerstone of environmental impact assessment and plays a critical role in protecting communities from the adverse effects of development projects.

What is human risk assessment? 🔗

Human risk assessment is a structured, science-based process that evaluates the likelihood and severity of adverse health effects resulting from human exposure to environmental hazards. These hazards can be chemical (like heavy metals or pesticides), physical (like radiation or noise), biological (like pathogens in water), or even socioeconomic (like limited access to healthcare).

The U.S. Environmental Protection Agency (EPA) defines risk as the chance of harmful effects to human health resulting from exposure to an environmental stressor. A stressor can be any physical, chemical, or biological entity capable of causing harm. The goal of human risk assessment is to answer critical questions: What hazards are present? Who is exposed? How much exposure is occurring? And what health effects might result?

This process is essential during the planning and execution of development projects – from industrial construction and waste disposal to urban expansion and agricultural intensification. Without it, communities may be unknowingly exposed to contaminants that cause chronic diseases, developmental disorders, or even death.

Key steps in the human risk assessment process 🔗

Human risk assessment follows a well-defined framework. The EPA’s four-step process is the most widely recognised model used globally. Each step builds on the previous one, creating a comprehensive picture of potential health threats.

Hazard identification 🔗

The first step involves determining whether exposure to a particular agent can cause specific health problems. Assessors examine scientific data – from clinical studies, epidemiological research, and animal testing – to establish whether a substance or condition can lead to effects like cancer, birth defects, respiratory illness, or neurological damage. For chemical stressors, this involves evaluating the weight of evidence linking the agent to adverse outcomes.

Dose-response assessment 🔗

Once a hazard is identified, the next step determines the relationship between the amount of exposure (dose) and the severity of health effects (response). This principle traces back to the foundational toxicology concept attributed to Paracelsus – that the dose determines the poison. As the dose increases, the observed health effects typically intensify. This step helps define thresholds below which exposure may be considered safe and levels at which harm becomes likely.

Exposure assessment 🔗

This step measures or estimates how much of a hazardous agent people are actually encountering. It looks at the frequency, duration, and intensity of exposure through different pathways – air, water, soil, food, or direct skin contact. It also considers which populations are exposed, including vulnerable groups such as children, pregnant women, the elderly, and workers in high-risk industries.

Risk characterisation 🔗

The final step combines the information from the previous stages to produce an overall estimate of risk. It includes both quantitative estimates (like the probability of developing cancer from a certain exposure level) and qualitative descriptions of uncertainty. Decision-makers use this information to determine whether action is needed to protect public health.

Factors influencing human risk 🔗

The risk to human health from environmental hazards is not uniform. Several interacting factors determine how severely a population or individual is affected.

Environmental hazards 🔗

Chemical contaminants are among the most studied environmental hazards. Industrial discharge, agricultural runoff, vehicle emissions, and improper waste disposal release substances like lead, arsenic, mercury, pesticides, and volatile organic compounds into the air, water, and soil. Radiation – both from natural sources like radon and from human activities such as nuclear energy – also poses significant health risks. Physical hazards like excessive noise, extreme heat, and particulate dust are common in construction, mining, and manufacturing settings.

Biological hazards 🔗

Biological agents, particularly waterborne pathogens, represent a major category of human health risk. Bacteria like Vibrio cholerae and Salmonella, parasites like Giardia and Cryptosporidium, and viruses such as hepatitis A thrive in contaminated water sources. According to the World Health Organization (WHO), contaminated drinking water can transmit diseases such as diarrhoea, cholera, dysentery, typhoid, and polio, and causes an estimated 505,000 diarrhoeal deaths annually.

Socioeconomic status 🔗

People in lower income communities often face disproportionately higher exposure to environmental hazards. They are more likely to live near industrial zones, lack access to clean water and sanitation, and have limited healthcare options. Poverty directly amplifies vulnerability – families in developing regions spend a significant share of their income on treatment when waterborne diseases strike. Socioeconomic factors also influence nutrition, which affects the body’s ability to resist the impacts of toxic exposure.

Individual vulnerability 🔗

Age, genetics, pre-existing health conditions, and lifestyle all influence how a person responds to environmental hazards. Children are especially vulnerable because their bodies are still developing, they consume more food and water relative to their body weight, and they engage in behaviours like hand-to-mouth contact that increase exposure. The EPA has developed specific frameworks for assessing health risks to children, recognising that standard adult-based assessments may underestimate risk to younger populations.

Risk management: identifying and controlling health risks 🔗

Risk assessment tells us what the dangers are. Risk management tells us what to do about them. It is the process of selecting and implementing strategies to reduce identified health risks to acceptable levels.

The hierarchy of controls 🔗

One of the most effective frameworks for managing health risks in workplaces and project sites is the hierarchy of controls, developed by the National Institute for Occupational Safety and Health (NIOSH). It ranks control measures from most effective to least effective.

Elimination is the top priority – removing the hazard entirely. For instance, a project might redesign a process to stop using a toxic chemical altogether. Substitution involves replacing a dangerous substance or process with a safer alternative, such as switching from solvent-based to plant-based inks. Engineering controls physically isolate workers from hazards. This includes ventilation systems that extract contaminated air, machine guards that prevent contact with moving parts, and enclosed systems that contain hazardous processes. According to the Occupational Safety and Health Administration (OSHA), employers should prioritise engineering solutions first, followed by safe work practices and administrative controls.

Administrative controls adjust how work is done – rotating workers to limit exposure duration, scheduling rest breaks, restricting access to hazardous areas, and providing training. Finally, personal protective equipment (PPE) such as gloves, respirators, hard hats, and safety goggles serves as the last line of defence. PPE is essential, but it requires consistent and correct use to be effective, making it less reliable than controls higher in the hierarchy.

Community-level risk management 🔗

Beyond workplaces, risk management extends to protecting surrounding communities. This includes environmental monitoring programmes that track air and water quality near industrial sites, buffer zones between residential areas and pollution sources, water treatment infrastructure, and public health surveillance systems that detect disease outbreaks early. Regulatory frameworks – such as environmental clearance requirements and emission standards – are essential tools that mandate risk assessment before development projects begin.

Common health hazards linked to development 🔗

Development projects – while necessary for economic growth – frequently introduce or intensify health hazards for nearby populations and workers.

Waterborne diseases 🔗

Construction, mining, and industrial operations often contaminate water sources through runoff, effluent discharge, and disruption of natural water systems. Waterborne diseases remain one of the most significant public health challenges globally. The WHO reports that around one million people die each year from diarrhoea linked to unsafe drinking water and poor sanitation. The situation is particularly severe in developing countries, where approximately 2.1 billion people lack access to safely managed drinking water services.

Common waterborne illnesses include cholera, typhoid fever, hepatitis A and E, and parasitic infections caused by Giardia and Cryptosporidium. These diseases spread through the faecal-oral route when drinking water or food is contaminated with human or animal waste. Children under five are disproportionately affected – diarrhoeal diseases are among the leading causes of childhood mortality globally.

Occupational health risks 🔗

Workers in construction, mining, manufacturing, and agriculture face a range of occupational health hazards daily. These include exposure to toxic dust (like silica and asbestos), chemical fumes, excessive noise, extreme temperatures, and ergonomic hazards from repetitive or heavy physical labour. Long-term exposure to these hazards can lead to respiratory diseases like silicosis and asbestosis, hearing loss, musculoskeletal disorders, skin conditions, and various forms of cancer.

The Canadian Centre for Occupational Health and Safety (CCOHS) emphasises that a comprehensive hazard control programme must include identification of all workplace hazards, proper training, exposure monitoring, and regular review of control measures. Without such programmes, workers – particularly those in informal or unregulated sectors – bear a heavy burden of preventable disease and injury.

Air pollution and respiratory illness 🔗

Development-related air pollution is a growing concern, especially in rapidly urbanising regions. Emissions from factories, vehicles, construction equipment, and power plants release particulate matter, nitrogen oxides, sulphur dioxide, and volatile organic compounds into the atmosphere. Prolonged exposure to these pollutants is linked to chronic respiratory conditions, cardiovascular disease, and premature death. Communities located downwind from industrial zones or near major highways are at the highest risk.

Chemical contamination of soil and food 🔗

Industrial activities and agricultural practices can introduce heavy metals, pesticides, and other persistent pollutants into soil. These substances enter the food chain through crops grown in contaminated land or through livestock that graze on affected pastures. Long-term ingestion of contaminated food can cause liver and kidney damage, neurological disorders, and developmental problems in children.

Why human risk assessment matters for sustainable development 🔗

Human risk assessment is not just a regulatory formality – it is a fundamental tool for ensuring that economic development does not come at the cost of public health. When conducted thoroughly and transparently, it provides the scientific basis for informed decision-making. It tells planners, regulators, and communities where the dangers lie and what can be done to prevent harm.

Integrating human risk assessment into environmental impact assessment processes ensures that health considerations receive the attention they deserve alongside ecological and economic factors. It supports the precautionary principle – taking preventive action in the face of uncertainty, rather than waiting for harm to occur before responding.

As development pressures intensify worldwide and environmental pollution becomes more complex, the need for rigorous, evidence-based human risk assessment will only grow. Strengthening the capacity for risk assessment – particularly in developing nations where the health burden from environmental hazards is heaviest – is critical for building healthier, more resilient communities.

What do you think? Should human risk assessment be made mandatory for all development projects, regardless of their scale? How can communities better participate in the risk assessment process to ensure their health concerns are heard and addressed?

References

1. https://www.epa.gov/risk/about-risk-assessment
2. https://www.epa.gov/risk/conducting-human-health-risk-assessment
3. https://www.who.int/news-room/fact-sheets/detail/drinking-water
4. https://www.epa.gov/risk/human-health-risk-assessment
5. https://www.cdc.gov/niosh/hierarchy-of-controls/about/index.html
6. https://www.osha.gov/safety-management/hazard-prevention
7. https://link.springer.com/article/10.1007/s43832-025-00198-x
8. https://www.ccohs.ca/oshanswers/hsprograms/hazard/hazard_control.html