Environmental Toxicology and Airborne Hazards Review

Comprehensive vocabulary flashcards covering airborne hazards, halogenated hydrocarbons, fundamentals of toxicology and pharmacokinetics, risk assessment principles, and water/soil pollution.

Particulates

Airborne pollutants consisting of particles or small droplets ranging in size between $0.01$ and $100\,\mu\text{m}$.

Aerosols

Suspensions of fine solid particles or liquid droplets in the air or another gas with particle sizes less than $10\,\mu\text{m}$.

Smog

A form of air pollution formed by a combination of smoke and fog.

Troposphere

The lowest layer of Earth's atmosphere, extending from sea level to approximately $10\,\text{miles}$ above sea level.

Stratosphere

The atmospheric layer located between $10$ and $30\,\text{miles}$ above sea level.

Biological Pesticides

Pest control substances—such as Bacillus thuringiensis and Lepidopteran pheromones—that have no known toxicity to humans, animals, or birds, and possess short biological half-lives.

Glyphosate Toxicity

Adverse toxic effects resulting from ingestion that include erosion and hemorrhage of the gastrointestinal tract.

Sulfur Dioxide ($\text{SO}_2$)

An airborne chemical compound that contributes directly to global cooling.

Halogenated Hydrocarbon

An organic compound bonded to at least one halogen (chlorine, bromine, fluorine, or iodine), characterized by high lipid solubility, stability under heat above $800\,^\circ\text{C}$, resistance to chemical breakdown, and toxicity to microorganisms.

TCDD (Tetrachlorodibenzodioxin)

A potent toxic halogenated compound that binds specific cellular receptors to alter protein synthesis, acts as an inducer of aryl hydrocarbon hydroxylase, and causes animal carcinogenesis.

Chloracne

A skin condition induced by exposure to halogenated hydrocarbons characterized by rash, cysts, and hyperpigmentation.

Polybrominated Biphenyls (PBBs)

Colorless, water-insoluble, lipophilic, and chemically stable compounds used as fire retardants in thermoplastics for television and office machine casings.

Polychlorinated Biphenyls (PCBs)

Lipophilic compounds used in insulators and brake linings that resist chemical breakdown, oxidation, acids, bases, and heat degradation up to $800\,^\circ\text{C}$.

Paraquat Exposure

Toxic herbicide exposure leading to pulmonary congestion, pulmonary edema, complete functional destruction of the lungs via pulmonary hemorrhage, and kidney or liver damage.

Acute Exposure

A toxic exposure characterized by single or limited doses whose effects are determined within $72\,\text{hours}$.

Chronic Exposure

Multiple low-level toxic exposures occurring over longer periods of time whose outcomes are evaluated at least $90\,\text{days}$ later.

Xenobiotic

Any substance, whether natural or anthropogenic in origin, that is foreign to living organisms.

Teratogenesis

The process by which physical, chemical, or biological agents disrupt normal embryonic or fetal development (e.g., DDT causing reproductive disruption).

$$\text{LD}_{50}$$

The individual dosage of a chemical agent that is calculated to kill $50\%$ of a population of test animals.

Pharmacokinetics

The study and characterization of the ways chemicals are absorbed, distributed throughout the body, biotransformed, and excreted.

Biotransformation Phase I

Metabolic reactions occurring primarily in the liver that convert lipophilic molecules into more polar forms by adding or revealing reactive functional groups ($-\text{NH}_2$, $-\text{OH}$, $-\text{SH}$, $-\text{COOH}$).

Biotransformation Phase II

Synthetic reactions that convert Phase I metabolites into substances that are more water-soluble and less biologically active.

Pharmacodynamics

The study of the biochemical and physiological actions that toxic chemicals or drugs exert on the body.

Agonist

A chemical that binds to a specific cellular receptor, mimics the action of an endogenous ligand, and initiates cellular activity (e.g., oxycodone at opioid receptors).

Antagonist

A substance that binds to a receptor without initiating a cellular biological response, effectively blocking agonist access (e.g., Narcan).

Oncogene

A gene that predisposes or alters a normal cell toward developing into a malignant cell.

Tumor Suppressor Gene

A normal gene responsible for slowing down cell division, repairing DNA errors, or triggering programmed cell death (apoptosis).

Complete Carcinogen

A toxic substance that can independently induce initiation, promotion, and progression stages of carcinogenesis (examples include asbestos, nickel, and cadmium).

Time-Weighted Average Exposure Value (TWA)

The average airborne concentration of a toxic agent to which a worker can safely be exposed over an $8\text{-hour}$ workday or $40\text{-hour}$ workweek.

Short-Term Exposure Value (STEV)

The maximum airborne concentration of a chemical agent to which a worker can be exposed continuously for a period of up to $15\,\text{minutes}$.

Ceiling Exposure Value

The absolute maximum airborne concentration of an occupational agent that must not be exceeded at any point during an exposure period.

No Observable Adverse Effect Level (NOAEL)

The highest tested dose or exposure level of a chemical at which no adverse biological effects are detected in experimental animals.

Acceptable Daily Intake (ADI)

The defined allowable environmental levels of contaminants across air, water, food, and noise exposure.

Linearized Multistage Assessment Technique

A risk model involving four major steps: evidence of mutagenesis, dosage calculation, calculating equivalent human dose, and determining maximum allowed limit.

De Minimis Concept

A regulatory principle asserting that if a calculated risk level is negligibly small, it does not warrant government or legal regulation.

Precautionary Principle

The regulatory guideline stating that in the presence of serious or irreversible threats, lack of full scientific certainty shall not delay cost-effective preventive action.

Acclimation

The adaptive process through which an organism adjusts physiological tolerances to a single environmental variable under laboratory or natural conditions.

Aquatic Dead Zones

Hypoxic water bodies devoid of dissolved oxygen caused by excessive nutrient runoff from agricultural fertilizers.

Bioaccumulation

The total uptake and net retention of dissolved and ingested forms of a toxicant directly into an organism's tissues.

Biomagnification

The sequential increase in the concentration of a chemical toxicant as it moves progressively upward through successive trophic levels in a food chain.

Chlorophenoxy Acid Herbicides

Herbicidal agents designed to mimic plant growth hormones, forcing rapid plant growth that rapidly depletes energy supplies and kills the plant.

Love Canal Disaster

An environmental disaster in which Hooker Chemical Company dumped over $300$ chemicals and $420{,}000\,\text{metric tonnes}$ of toxic waste that leached into the surrounding soil, resulting in basement chemical odors, collapsing ground, physical illnesses, and elevated rates of depression and suicide attempts.