Principles of Toxicology and Risk Assessment

Toxicology

Study of harmful effects of chemicals on organisms.

Common toxicants around the home

ibuprofen, gas, rubbing alcohol, bleach, cleaning agents

Risk Assessment

Process to evaluate potential health risks from exposures.

Immediate Effects

Rapid adverse reactions to toxic substances.

Delayed Effects

Adverse reactions occurring after a period of time.

Local Effects

Toxic effects occurring at the exposure site.

Systemic Effects

Toxic effects affecting the entire body or organ systems.

LD50

Dose killing 50% of test animals within a time frame.

Dose-Response Relationship

Correlation between dose and severity of toxic effects.

How do toxicants work?

bind to enzymes and other important molecules, altering cellular function

Factors Affecting Toxicity

Includes route of entry, dose, and exposure duration

Chemical Routes of Entry

inhalation, ingestion, dermal.

Inhalation

Fastest route for toxicant entry into the body.

Dermal Absorption

Slowest route for toxicant entry into the body.

Reactivity

Chemical property influencing its potential toxicity.

Bioaccumulation

Build-up of toxic substances in tissues or organs.

Food Chain Concentration

Toxicants increase in concentration through food webs.

Who are most susceptible to toxins?

young, sick, and elderly

Chemical Knowledge Gaps

Insufficient data on many chemicals' effects.

Cumulative Toxicity

Effects of multiple exposures over time.

Bioaccumulation

Accumulation of substances in living organisms.

Biological magnification

Increase in substance concentration up the food chain.

Additive response

Combined effect equals the sum of individual effects. 2+2=4

Additive response example

acetaminophen and aspirin

Synergistic response

Combined effect exceeds the sum of individual effects. 2+2=6

Synergistic response Example

barbituates and alcohol; tobacco and asbestos

Potentiation

Non-toxic chemical enhances toxicity of another. 0+2=6

Potentiation example

isopropanol and carbon tetrachloride

Antagonistic response

Combined effect reduces the harmful impact of chemicals. 2+4=3

Antagonistic response example

naloxone and opioids

Carcinogens

Substances that can cause cancer after repeated exposure.

Biotransformation

Chemical alteration of substances by body enzymes.

Teratogens

Agents causing structural or functional birth defects.

Organogenesis

Critical period of organ development in embryos.

Reproductive Toxicity

Interference with reproductive processes by agents.

Environmental hormones

Herbicides, Dioxins, Nonylphenols, Phthalates

Incidence of Down Syndrome

Linked to maternal age and chromosome abnormalities.

Asbestos

Mineral fiber linked to respiratory diseases including pulmonary fibrosis, lung cancer, and mesothelioma

Chemical agents

Substances that can cause harmful biological effects.

Physical agents

Environmental factors causing biological harm.

Biological agents

Living organisms that can cause health issues.

ELF Magnetic Fields

Extremely low-frequency fields from electricity flow.

Cancer Incidence

Rate of new cancer cases in a population.

Toxic Substances Control Act

U.S. law to manage harmful chemicals. seeks to prevent the introduction of chemicals that will be harmful and eliminate those already in use that pose an unacceptable risk

End-of-Pipe Controls

Pollution control measures applied after pollution occurs.

Pollution Prevention

Strategies to eliminate hazardous waste production.

Market Incentives

Economic strategies to encourage safer chemical use.

Innovation Promotion

Encouraging new solutions to reduce pollution.

Integrated Pollution Control

Regulating multiple pollution sources simultaneously.

Risk Identification

First step in risk assessment to recognize hazards.

Probability Determination

Second step assessing likelihood of risk occurrence.

Severity Assessment

Evaluating potential impacts of identified risks.

Risk Acceptability

Determined by perceptions and societal values.

Cost-Benefit Analysis

Weighing costs against benefits to assess risk.

Sustainable Development

Minimizing costs while maximizing benefits for society.

Values in Decision Making

Personal beliefs influencing risk perception and choices.

Long-Range View

Perspective considering global sustainability over time.