What is the environment?

An organism's environment is the environment in which it lives and has an impact on its well-being. The World Health Organization (WHO) defines environmental health as "those aspects of public health, such as quality of life, that are influenced by physical, chemical, biological, social, and psychosocial components in the environment." Environmental health is concerned with both natural and man-made settings in order to enhance public health. Environmental science, occupational medicine, toxicology, and epidemiology are the key subdisciplines of environmental health.

Environmental health disciplines

There are five basic disciplines that generally contribute to the field of environmental health. They are:

Environmental epidemiology 

Environmental epidemiology is one of the environmental health fields. Environmental epidemiology: The study of the relationship between environmental exposures such as chemicals, radiation, and microbiological organisms and population health is known as environmental epidemiology. Because humans cannot ethically be exposed to chemicals suspected of causing disease, environmental epidemiology relies heavily on observational studies, which merely record exposures that people have already had. While the inability to use experimental study designs is a constraint of environmental epidemiology, this field focuses on human health rather than predicting effects from animal studies.

Exposure science

Exposure science, which involves both identifying and analyzing exposures, is used to investigate human exposure to environmental pollutants. Exposure science can help support environmental epidemiology by identifying common exposures whose health outcomes may be better understood through a toxicology study or determining whether current levels of exposure may exceed recommended levels through a risk assessment. Exposure science can also help support environmental epidemiology by identifying common exposures whose health outcomes may be better understood through a toxicology study.


Toxicology is the study of how environmental exposures generate specific health effects in animals with the goal of understanding potential human health repercussions. Because animal subjects can be employed, toxicology offers the advantage of being able to conduct randomized controlled trials and other experimental investigations. However, there are numerous differences between animal and human biology, making it difficult to assess the findings of animal studies in terms of their relevance to human health.

Environmental law

Environmental law is a body of treaties, legislation, regulations, and common and customary standards that deal with the effects of human activity on the natural environment. Data from epidemiology, toxicology, and exposure science can be used to conduct risk assessments for single chemicals, chemical mixtures, or other risk variables in order to determine whether an exposure offers a significant danger to human health. This information can be used to establish and carry out environmental health strategies.

Environmental engineering

Environmental engineering uses scientific and technical principles to protect human populations from harmful environmental variables, protect environments from potentially harmful consequences of natural and human activities, and improve overall environmental quality.

Factors affecting environmental health

Maintaining a healthy environment is critical to boosting one's quality of life and number of years of healthy life. Environmental factors account for 23% of all deaths worldwide and 26% of deaths among children under the age of 5. Environmental influences include the following:

  • exposure to a hazardous substance in the air, water, soil, and food.
  • Climate change.
  • Occupational hazards.
  • built environment.

Exposure to hazardous substances

Chemical hazards occur when chemicals are mismanaged posing an unacceptable health risk to humans. Almost every activity produces waste in the environment such as exhaust gases, solid and hazardous waste. Chemicals can travel via the air, soil, and water, and can also be found in plants and animals, resulting in contamination of the air we breathe, the food we eat, and the water we drink. Premature death, cancer, and long-term harm to the respiratory and cardiovascular systems have all been related to poor air quality. Exposure can occur when people breathe hazardous chemical vapor or air that is contaminated by chemical dust. Sulfur dioxide, carbon monoxide, and nitrogen dioxide are the major chemical pollutants on the Earth. Heart disorders, asthma can cause by air pollution.

What are environmental health hazards?

Environmental hazards are substances, a state, or an event that have the potential to endanger the natural environment or negatively impact public health, such as storms and earthquakes. Pollutants include heavy metals, pesticides, biological contaminants, hazardous waste, industrial and household chemicals, and any single or combination of dangerous chemical, biological, or physical agents in the environment as a result of human activities or natural processes. Environmental health hazards are chemical, physical, or biological factors in our environment that can cause health risks to human beings. Exposure to these factors causes severe health problems and can even cause death.

What is exposure?

The contact between an agent and a target is characterized as exposure in this context. Throughout an exposure period, contact occurs at an exposure surface. As much as possible, exposure evaluation to environmental health hazards is required for both etiologic diagnoses of occupational disorders and worker health surveillance. The evaluation can be carried out using either fixed or personnel samplers to measure the substance's concentrations in the air.

Route of exposure

There are four primary routes of exposure to chemical contaminants, they are inhalation via breathing such as dust, fumes, mist, and smoke. Absorption through skin contact and ingestion through food, drinking water, and other liquids. The exposure of chemical factors through the water like drinking water can cause health risks. The injection is the fourth route of exposure.

Measurement of exposure to physical agents

The physical agent is one of the environmental health hazards. They are sources of energy that can cause injury or sickness. Physical agents such as noise, vibration, and ionizing and non-ionizing radiation are increasingly being used to safeguard the environment and human health. Exposure to physical agents can affect mental ability. In the most severe situations, they can result in disability. The impact of these environmental hazards is usually felt in the workplace and is dependent on the severity of the factor, the length of exposure can cause health risks for humans. Exposure to physical agents can cause several health risks such as visual trouble, musculoskeletal disorders, bone damage, fatigue, skin cancers, and reproductive organ damage.

Measurements of exposure to chemical agents

Chemicals are widely used in industry and our daily lives. Chemical agents are one of the most dangerous environmental hazards. Types of chemical agents such as liquid forms like acids, vapors, and fumes. Exposure to these environmental hazards can cause health risks. Chemical neurotoxins, immunological agents, carcinogens, and sensitizers are only a few examples of dangerous chemicals. Pesticide is a chemical agent, exposure to pesticides can cause severe symptoms such as skin allergy, asthma, and dizziness. Some pesticides such as organophosphate are dangerous to human health. Long-term exposure to substances including silica dust, engine exhaust, and tobacco smoke has been linked to an increased risk of heart disease, stroke, and hypertension.

Measurement of exposure of biological agents

Bacteria, viruses, fungi, and other microbes, as well as their poisons, are biological agents. They have the potential to harm human health in a variety of ways, ranging from minor allergic reactions to life-threatening medical disorders and even death. Anthrax, avian-flu, and bloodborne pathogens are examples of biological agents.

Occupational diseases

Chemical agents are the most common environmental hazards that might result in occupational diseases, accounting for 41 of the occupational diseases induced by exposure to agents from work activities. Occupational disease can be caused by exposure to environmental hazards. Acute and chronic occupational diseases exist. Allergic skin disease, occupational cancer, and acute poisoning are examples of occupational illnesses. These are caused by the overuse of pesticides in the workplace. Long-term exposure to environmental hazards such as physical agents, chemical agents, and biological agents can create severe health problems.

How can hazards be managed?

Monitoring and control approaches are used to manage the impact of environmental threats. The risk of hazards can be reduced by establishing and conducting systematic measurements to monitor changes in the environment or public health, promoting early detection and intervention.

Context and Applications

This topic is important for postgraduate and undergraduate courses, particularly for

  • Bachelors of Science in biology
  • Bachelors of Science in environmental science
  • Masters of Science in public health

Practice Problems

Question 1: How many types of environmental health hazards are there?

  1. One
  2. Three
  3. Four
  4. Two

Answer: Option 2 is correct.

Explanation: Physical dangers, chemical hazards, and biological hazards are the three forms of health hazards. Global warming, UV radiation, radioactivity, and other physical threats exist. Chemical dangers include the use of fossil fuels, insecticides, heavy metals, and other chemicals. Bacteria, viruses, and other biological dangers are examples of biological hazards.

Question 2: How do pollutants reach humans?

  1. By internal factor
  2. By external factor
  3. By injection
  4. All of the above.

Answer: Option 1 is correct.

Explanation: Pollutants enter our bodies through the food, drinking water, and the air we breathe, putting our health at risk in both the short and long term.

Question 3: What type of hazards does toxicology deal with?

  1. Biological
  2. Physical
  3. Chemical
  4. Ergonomically

Answer: Option 3 is correct.

Explanation: Toxicology has come under the chemical agent. Types of chemical agents such as liquid forms like acids, vapors, and fumes. Gases, metals, and dust are the types of chemical agents. These chemical agents can cause major problems in public health.

Question 4: Which of the following pairings of gases is the major contributor to greenhouse gas emissions?

  1. Carbon dioxide and nitrous oxide
  2. Carbon dioxide and carbon monoxide
  3. Chlorofluorocarbons and Sulphur dioxide
  4. Carbon dioxide and ozone

Answer: Option 1 is correct.

Explanation: Greenhouse gases are carbon dioxide, methane, nitrous oxide, and other gases that accumulate in the atmosphere and form the heat-reflective layer that keeps the Earth at a habitable temperature.

Question 5: BOD stands for _____________.

  1. Biotic oxidation demand
  2. Biological oxidation demand
  3. Biochemical oxygen demand
  4. Biological oxygen demand

Answer: Option 4 is correct.

Explanation: The amount of oxygen absorbed by bacteria and other microorganisms during the aerobic decomposition of organic materials.

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