Chapter 17

Hazards and Risks

Questions for Today

• What is Risk and how do we handle Risk?• What is a Hazard?• What is Toxicology?• What affects Toxicity?• How do we determine Lethality?

What is Risk?

• Risk: the probability of suffering harm from a hazard that can cause injury, disease, death, economic loss, or damage.– Expressed in probability (Lifetime Probability)– For instance:

• The Lifetime probability of developing lung cancer from smoking one pack of cigarettes per day is 1 in 250

– 1 person out of 250 people that smoke one pack a day will develop lung cancer in a human lifetime, roughly 70 years.

How do we handle Risk?

• Risk Assessment: the scientific process of using statistical methods to estimate how much harm a particular hazard can cause to human health or to the environment.– A prioritizing tool.– Which risk is worse?

• Risk Management: deciding whether or how to reduce a particular risk to a certain level and at what cost.– Preventative Strategy– What can I do to lower the hazards associated with this risk?

Risk Analysis: involves indentifying hazards and evaluating their associated risks, ranking risks, determining options and making decisions about reducing or eliminating risks and informing decision makers and the public about risks.

Assessment of Risks by the public

• Due to sensational media and other highly opinionated sources, many people have a hard time analyzing risks that they see.– Avian Flu and Swine Flu– Education is the Key to understanding risk and hazards

Types of Hazards

• Types of Hazards:– Biological Hazards: Pathogens and infectious disease– Chemical Hazards: organic or inorganic chemicals in our

air, soil, food, water and food– Physical Hazards: fire, earthquakes, volcanic eruptions,

flood, and storms– Cultural Hazards: unsafe working conditions, highways,

criminal assault, poverty– Lifestyle choices: smoking, eating too much or too little,

and too much alcohol.

Hazards can be multiple in nature

• A situation can be classified with more than one hazard.– Smog: Chemical and Cultural– Industrial runoff: Biological and Chemical.– Depends on the situation.

Toxicity

• Toxicology: the study of the harmful effects of chemicals on humans and other organisms.– The study of poisons

• Toxicity: a measure of how harmful a substance is

Principles of Toxicology

• Basic Principle of toxicology: any synthetic or natural chemical can be harmful if ingested in a large enough quantity.– Dose equals poison

• Dose: the amount of harmful chemical that a person has ingested, inhaled, or absorbed through the skin.

Principles of Toxicology

• Age and genetic makeup can affect toxicity.– Children and the elderly are usually affected more by toxins than

adults• Multiple Chemical Sensitivity

– The way your body handles toxins• Detoxification

• Solubility affects toxicity– Water soluble toxins can dissolve in water supplies and rivers and

can enter your body, but will eventually pass out.– Fat Soluble toxins can penetrate cell membranes and can be stored

in fat cells in the body. • This is much more harmful to the body

Principles of Toxicology

• Persistence: the resistance of toxins to breakdown.– DDT and PCBs

• Biological Magnification: when toxins magnify through the trophic levels: Getting more and more concentrated.– DDT and PCBs

Principles of Toxicology

• Response: damage to health resulting from exposure to a chemical– Acute effects: immediate or rapid harmful reaction to an

exposure• High doses in a small period of time

– Chronic effect: a permanent long-lasting consequence• Low doses over a long period of time

How do we determine the lethality of chemicals?

• Animal testing is a necessary step in order to determine the lethality of toxins for humans.– We use lab mice and rats because they are mammals

and their body systems react similarly to ours.

• Scientist estimate the lethality by plotting the results of their tests on dose-response curve.– Median Lethal Dose (LD50) Curve

• The dose that can kill 50% of the animals in a test population within an 18-day period.

LD50

Dose Response Models

• Two types dose-response models– Nonthreshold dose-response – The more toxin in your

system the more its going to affect you (Linear No-Threshold)

• Radiation

– Threshold dose-response – you won’t feel the effects of the toxin until it reaches a certain threshold.

What are Lethal Doses to Humans?

Toxins can be found anywhere