Environmental Hazards and Human Health

Are Baby Bottles & Food Cans Safe To Use? 1.Some synthetic chemicals act as hormone mimics and disrupt the human endocrine system 2. Excess estrogen effects on males  Feminization  Smaller penis  Lower sperm counts

The BPA Controversy 1. BPA (bisphenol A)  Estrogen mimic  Found in In polycarbonates and other hardened plastics such as:  Baby bottles and sipping cups  Reusable water bottles  Sports drink and juice bottles  Microwave dishes  Food storage containers  Liners of most food and soft drink cans

The BPA Controversy 1. BPA leaches into foods and drinks  Even when containers not heated 2. 93% of Americans older than 6 have BPA levels above the threshold level set by the EPA  Higher in children and adolescents 3. Risks for infants, children, adults

Risks Are Usually Expressed as Probabilities 1. Risk depends on the following factors  How much of a chemical is present in an environmental medium (e.g., soil, water, air),  How much contact (exposure) a person or ecological receptor has with the contaminated environmental medium, and  The inherent toxicity of the chemical. 2. Risk Assessment  Uses statistical methods to estimate how much harm a particular hazard can cause to human health or to the environment

Science: Risk Assessment and Risk Management Fig. 17-2, p. 437

Types of Hazards 1. Biological: Pathogen: an organism that causes disease in other organisms 2. Chemical: harmful chemicals in air, water, soil, food, & human made products 3. Natural: natural disasters 4. Cultural: unsafe working conditions, unsafe highways 5. Lifestyle choices: smoking, alcohol consumption, high fat food, etc

Disease 1. Infectious disease:  Caused by a pathogen invades the body & multiplies 2. Transmissible disease  Contagious or communicable disease  Infectious disease transmitted between people  Flu, tuberculosis, measles 3. Non-transmissible disease  Not caused by living organisms  Heart disease, most cancers, diabetes 4. Since 1950, death from infectious diseases have declined due to  Better health care  Better sanitation  Antibiotics  Vaccines

Infectious Diseases Are Still Major Health Threats 1. Infectious diseases spread through  Air  Water  Food  Body fluids 2. Epidemics and pandemics 3. Resistance of bacteria and insects to drugs and pesticides

Pathways for Infectious Diseases in Humans Fig. 17-3, p. 439

Major Causes of Death from Infectious Diseases in the World 2007 Fig. 17-4, p. 439

We Can Reduce the Incidence of Infectious Diseases 1. Good news  Vaccinations on the rise  Oral rehydration therapy 2. Bad news  More money needed for medical research in developing countries

Solutions: Infectious Diseases Fig. 17-8, p. 445

Some Chemicals Can Cause Cancers, Mutations, & Birth Defects 1. Carcinogens include:  Chemicals, types of radiation, or certain viruses the cause or promote cancer 2. Mutagens  Chemicals or radiation that cause mutations or increase their frequency 4. Teratogens  Chemicals that cause harm or birth defects to a fetus or embryo  EX: Alcohol causes fetal alcohol syndrome

Potential Pathways on Which Toxic Chemicals Move Through the Environment Fig. 17-9, p. 447

Some Chemicals May Affect Our Immune & Nervous Systems 1. Some natural and synthetic chemicals in the environment can weaken and harm  Immune system  Nervous system  Neurotoxins: PCBs, arsenic, lead, some pesticides  Endocrine system

Some Chemicals Affect the Human Endocrine System 1. Glands that release hormones that regulate bodily systems and control sexual reproduction, growth, development, learning, behavior 2. Hormonally active agents have similar shapes and bind to hormone receptors  Gender benders  Thyroid disruptors  BPA?  Phthalates in plastics

Hormones & Hormones Mimics Each type of hormone has a unique molecular shape that allows it to attach to specially shaped receptors on the surface of, or inside, cells and to transmit its chemical message (left). Molecules of certain pesticides and other synthetic chemicals have shapes similar to those of natural hormones, allowing them to attach to the hormone molecules and disrupt the endocrine system in people and various other animals.

Factors That Determine the Harmful Health Effects of a Chemical 1. Toxicology: the study of the harmful effects of chemicals on humans or other organisms; study of poisons 2. Toxicity: measure of the harmfulness of a substance or its ability to cause injury, illness, or death 3. Toxicity is dependent on dependent on  Dose: amount ingested, inhaled, or absorbed  Age: greater effects on fetus than on adults  Genetic makeup: some individuals are more sensity than others  How well the body’s detoxification system works

Many Factors Determine the Harmful Health Effects of a Chemical (1) Toxicology Toxicity dependent on –Dose –Age –Genetic makeup –Multiple chemical sensitivity (MCS) –Solubility –Persistence –Biomagnification

Variables that Affect the Level of Harm 1. Solubility: water soluble verses fat soluble 2. Persistence: resistance to breakdown  DDT & PCBs have high resistance because they do not breakdown very easily 3. Biomagnification: organisms higher up on food chain are more susceptible

Hypothetical Dose-Response Curve Showing Determination of the LD50 1. LD50 is the lethal dose that kills 50% of the individuals. 2. Important for determining the relative toxicity of a chemical. 3. LD50 studies done on lab animals (rats & mice) & results are extrapolated to humans

Synergistic Interaction Synergistic Interactions: when two risks together cause more harm than on would expect based on their individual risks. EX: the health impact of the carcinogen, asbestos, can be much higher if the individual is also a smoker