9.1 An Overview of Environmental Health Environmental health: the study of how environmental factors affect human health and our quality of life Hazards: factors that threaten or are harmful to human health Pathogens: disease-causing agents Types of Environmental Health Hazards: Biological: Viruses, bacteria,& other organisms that cause disease Ex: flu virus, pet dander Social: Lifestyle choices, jobs, & locations that endanger our health Ex: smoking, bad diet, living next to a factory Chemical: Harmful artificial & natural chemicals in the environment (two types: synthetic and hazardous) ex: disinfectants Physical: Natural disasters and ongoing natural phenomena Ex: UV radiation, that can cause health problems Epidemiology: Epidemiology: The study of disease in human populations—how and where they occur and how they can be controlled - Often involves studying large groups over long periods Can determine statistical associations between health hazards and effects, but can’t prove the hazards actually caused the effects Toxicology: Toxicology: the study of how poisonous substances affect an organism’s health Toxicity: a measure of how harmful a substance is - Toxicity depends on 2 things: 1- What the substance is 2- how much of the substance is needed to cause harm Dose-response relationships: Toxicologists look at toxicity by determining dose-response relationships Dose: the amount of a substance an organism is exposed to Response: the effect an organism shows as a result of exposure Dose-response relationship: the relationship between the different doses and the responses they generate Ex: if you are exposed to an extremely high dose of radiation the response can be death Threshold dose: responses above certain doses Individual Responses: Sensitivity to hazards varies with age, sex, weight, and immune system health - Fetuses, infants, and young children tend to be more sensitive to harmful chemicals than adults are Many diseases have genetic as well as environmental factors - Both a person’s genes and the environment they live in can affect the individual’s chances of suffering from the disease Risk Assessment: Risk: The probability that a hazard will cause harm Risk assessment: The process of measuring risk Takes into account: - The type of hazard - How frequently humans will be exposed to it - How sensitive people are to it Scientists use risk assessments to help them make decisions about which hazards may be harmful - Policymakers can use risk assessments to help them shape policies that protect both the people and the environment What steps does a scientist have to take when doing a risk assessment for a chemical hazard? - Identify the possible hazard - Determine its toxicity - Determine the extent that humans will be exposed to it 9.2 Biological and Social hazards Infectious diseases: Diseases caused by pathogens - Spread by human and animal contact and through contaminated food and water - Cause of almost half of all deaths in developing nations Covering your mouth when you cough, washing your hands often, and staying home from school if you’re sick helps prevent the spread of infectious disease Infectious diseases spread by humans: Some diseases are spread directly from one human to another Ex: touching, biting, sexual intercourse, contact with bodily fluids, and inhaling expelled droplets can all spread disease AIDS: can be transmitted when a person comes in contact with the blood or bloody fluids of an infected person Tuberculosis: is spread through droplets in the air by coughing, sneezing, speaking, or spitting Infectious diseases spread by water or food: Some pathogens spread when people consume contaminated water or food cholera: a waterborne pathogen that contaminates the water supply when a person drinks contaminated water (by human feces and vomiting) Infectious diseases spread by other organisms: Diseases can also be spread by other organisms The organism carries the pathogen and passes it to a person Malaria: a mosquito picks up the pathogen when it bites an infected person and transmits it when it bites a non-infected person Vectors: disease-carrying organisms Ex: mosquitoes and ticks Emerging Diseases: Emerging diseases: Diseases appearing in the human population for the first time or suddenly beginning to spread rapidly - They spread faster than infectious diseases - Humans have little or no resistance, and no vaccines have been developed They can be spread by humans, organisms and food or water Factors that spread emerging diseases: - increasing human mobility - growing antibiotic resistance - environmental changes Responding to Emerging Diseases: World Health Organization (WHO): Monitors health events worldwide and coordinates international responses to emerging diseases Centers for Disease Control and Prevention (CDC): Responds to emerging diseases in the United States; the CDC developed pandemic plans to deal with the spread of the COVID-19 virus. Pandemic: an outbreak that becomes widespread and affects a whole region, continent, or the world International and government agencies and organizations work together to help monitor, respond to, and control the spread of emerging diseases Social Hazards: Social hazards: lifestyle choices that harm your health - Some social hazards are easier to avoid than others Some social hazards can be reduced by changing your behavior Ex: eating healthier foods, staying active and fit can help you avoid obesity, heart disease, and high blood pressure Examples of social hazards: - smoking - being exposed to secondhand smoke - living near an old toxic waste site - working with harmful chemicals - eating fatty foods How may climate change increase the spread of disease? If global temperatures continue to rise, tropical diseases could expand into new, formerly cooler areas 9.3 Toxic Substances in the Environment Chemical hazards: any chemical that may harm human health - Any chemical can be harmful in large enough amounts. Pollution: matter or energy that is released into the environment, causing negative effects that impact people, wildlife, and other aspects of the environment. Chemical hazards are not necessarily pollutants, and pollutants are not necessarily chemical hazards - Chemical hazards include chemicals that are not pollutants Types of Chemical Hazards: Carcinogens: Cancer-causing chemicals Chemical mutagens: Chemicals that cause genetic mutations Teratogens: Chemicals that harm embryos and fetuses Neurotoxins: Chemicals that affect the nervous system Endocrine disruptors: Chemicals that interfere with the endocrine system Allergens: Chemicals that over-activate the immune system Indoor Chemical Hazards: - Asbestos: a mineral that forms long, thin fibers - Radon: highly toxic radioactive gas - VOC: Volatile organic compounds (carbon monoxide, lead) Sources of Outdoor Chemical Hazards: In the air: Natural sources, such as volcanic eruptions, or human sources, such as pesticides In the ground: Pesticide use, improper disposal of electronics, etc. In the water: Chemical runoff from land or direct drainage of toxic substances into water Bioaccumulation and Biomagnification: - How long a chemical lasts or persists, can be a major concern for environmental scientists Organisms absorb, breathe, and ingest toxic substances from their environments; if these chemicals are persistent or last a long time, organisms may end up storing them in their bodies. Bioaccumulation: The buildup of toxic substances in the bodies of organisms (ex: DDT in fat methyl mercury in muscle) Biomagnification: The increased concentration of toxic substances with each step in a food chain Persistent organic pollutants are biomagnified and stay in the environment for long periods of time and over long distances.
