When evaluating potential hazards, you identify anything in an environment that has the capacity to cause harm, along with the specific conditions that determine how likely that harm is to occur and how severe it could be. This means identifying the source of danger itself, who or what it could affect, the ways people come into contact with it, and the factors that make an incident more or less probable. The process applies across workplaces, chemical exposures, environmental assessments, and public safety planning.
Hazards vs. Risks: A Key Distinction
The first thing identified in any hazard evaluation is the hazard itself, which is any source of potential damage, harm, or adverse health effects. A hazard is the agent responsible for potential harm. A chemical solvent sitting in an open container is a hazard. Wet floors, loud machinery, airborne dust, and infectious pathogens are all hazards.
Risk is different. Risk is the probability that someone will actually be harmed by a given hazard. A toxic chemical locked in a sealed cabinet still qualifies as a hazard, but the risk to workers is low because exposure is unlikely. That same chemical in an open, poorly ventilated room presents a much higher risk. Hazard evaluation requires identifying both: the thing that could cause harm and the likelihood that it will.
Categories of Hazards
Hazards are grouped into well-established categories. OSHA breaks workplace hazards into the following types:
- Chemical hazards: solvents, adhesives, paints, toxic dusts, and other substances that can damage tissue or organs through exposure.
- Physical hazards: noise, radiation, extreme heat or cold, vibration, and other environmental forces that can injure the body.
- Biological hazards: bacteria, viruses, mold, and other organisms that can cause infectious disease.
- Ergonomic hazards: heavy lifting, repetitive motions, awkward postures, and prolonged vibration that damage muscles, joints, or nerves over time.
- Safety hazards: slip and fall risks, electrical dangers, unguarded machinery, fire risks, and poor housekeeping.
Each workplace generates its own specific list. A manufacturing facility might focus on pinch points in machinery and lockout/tagout procedures for stored energy. A hospital evaluates needle sticks, patient handling injuries, and chemical disinfectants. The categories serve as a starting framework, not an exhaustive checklist.
Psychosocial Hazards
Not all hazards are physical. Psychosocial hazards are factors in a work environment that cause stress, strain, or interpersonal harm. These include work overload, inadequate staffing, lack of job training, shift work, role ambiguity, poor relationships with supervisors or coworkers, and lack of work-life balance. A 2019 American Nurses Association survey of more than 20,000 nurses found that 79% identified stress as the number one job hazard, 53% said they needed to work through breaks to complete their duties, and 27% reported workloads that were too heavy.
Workplace violence, bullying, and incivility also fall under psychosocial hazards. In that same survey, 24% of nurses reported verbal or nonverbal aggression from people in higher authority positions, 31% experienced it from peers, and 34% faced verbal or physical threats from patients or family members. These hazards produce measurable effects: irritability, depression, job dissatisfaction, and chronic stress that compounds over time.
Exposure Pathways
Identifying a hazard is only part of the evaluation. You also need to determine how people come into contact with it. The Agency for Toxic Substances and Disease Registry identifies four primary routes of exposure:
- Ingestion: swallowing contaminants through water, soil, or food.
- Inhalation: breathing in dust, vapor, gas, or other airborne contaminants. This includes chemicals that evaporate from water or soil surfaces.
- Dermal contact: skin exposure to contaminants in soil, water, sediment, or waste material.
- External radiation exposure: certain types of radiation (beta particles and gamma rays) can penetrate skin without direct contact, while others (alpha particles) require entry through wounds or damaged skin.
Knowing the exposure route shapes the entire response. A chemical that poses a hazard only through prolonged skin contact requires different controls than one that becomes dangerous the moment it becomes airborne. The evaluation process maps these pathways to determine where protective measures need to go.
How Hazards Are Systematically Identified
A Job Hazard Analysis, one of the most common formal tools, works through a structured sequence. First, you select the job or task to evaluate. Then you break the job into individual steps, documenting each action a worker performs. Videos and photos are often used to capture details that written descriptions miss.
For each step, you identify every associated hazard. This includes reviewing previous injury and illness records and considering worst-case scenarios. Then each hazard gets described in detail by answering specific questions: Who does it affect? What causes it? What contributing factors make it worse? When is it most likely to cause harm? Where does the operation take place? Why would an incident occur? This level of specificity transforms a vague concern (“the machine is dangerous”) into actionable information (“the blade guard is removed during cleaning, exposing the operator’s hands to a laceration hazard for approximately three minutes per shift”).
Severity and Likelihood Scoring
Once hazards are identified and described, each one gets evaluated on two dimensions: how bad the outcome could be, and how likely it is to happen. These two scores combine into an overall risk rating that determines which hazards get addressed first.
Severity is typically scored on a four-level scale:
- Catastrophic: could cause death or total loss of a facility.
- Critical: could cause severe injury, serious illness, or major property damage.
- Marginal: could cause minor injury, minor illness, or limited property damage.
- Negligible: presents minimal threat to safety, health, or property.
Likelihood follows a five-level scale ranging from “frequent” (continuously encountered during operations) down through “probable,” “occasional,” “remote,” and “improbable” (encountered only rarely, with chances possible but unlikely). Plotting severity against likelihood on a matrix produces a risk score. A catastrophic hazard that occurs frequently demands immediate action, while a negligible hazard that occurs rarely may simply be monitored.
Chemical Hazard Classification
Chemical hazards receive their own specialized evaluation through the Globally Harmonized System (GHS). This framework classifies chemicals based on the type and strength of evidence for specific health effects. For cancer-causing potential, classification criteria align with the International Agency for Research on Cancer and the National Toxicology Program, using the weight of available scientific evidence to assign a hazard category.
For skin effects, the GHS uses a tiered approach: existing human data takes priority, followed by animal data, then laboratory test data, then other sources. For organ damage from repeated exposure, expert judgment weighs all available evidence, with human data recognized as the most reliable source. Chemicals that sensitize the respiratory system are classified based on evidence that they trigger immune reactions after being inhaled, drawn from either human cases or validated animal studies. Each classification results in standardized hazard statements and pictograms that appear on labels and safety data sheets, giving workers and emergency responders immediate information about what a substance can do.
What the Evaluation Produces
The end product of hazard evaluation is a prioritized inventory. Each identified hazard has a description, a severity rating, a likelihood rating, a combined risk score, and the specific people or assets it threatens. This inventory drives decisions about engineering controls (physically removing or containing the hazard), administrative controls (changing procedures, schedules, or training), and personal protective equipment. The hazards scoring highest on the risk matrix get resources first. Lower-scoring hazards are documented and revisited on a regular cycle or whenever conditions change, such as new equipment, new chemicals, or changes in staffing patterns.