Chapter 3: Environmental Toxicology

Antagonism

2 chemicals administered together interefere with each other's action or one interferes with the action of the other

Indirect Effect of Toxic Exposure

A change in the function of the body's biochemical processes

How can measures of lethality maybe not describe fully a chemical's spectrum of toxicity?

A chemical may be low toxic, but have the effect of carcinogenicity

Carcinogen

A chemical or substance that causes or is suspected of causing cancer

Sub-Threshold Phase of a Dose-Response Curve

A flat portion of a curve suggesting that at low levels an increase in dosage produces no effect

Toxic Substance

A material that has toxic properties

What is toxicity related to?

A material's physical and chemical properties

What 2 things must you know in order to understand a chemical's toxicology?

Effects of the chemical At what levels of exposure the chemical becomes hazardous to humans

National Toxicology Program (NTP)

Emphasizes the central role of toxicology in identifying the potential hazards of chemicals used in the US

Specializations of toxicology relevant to environmental health

Environmental toxicology Reproductive toxicology Developmental toxicology

Reproductive Toxicology

Examines the association between chemicals and adverse effects upon the reproductive system

Hazard Assessment

Examines the evidence that associates exposure to an agent with its toxicity and produces a qualitative judgment about the strength of the evidence

Inorganic Toxin

Specific chemicals that have not been extracted form living organisms and do not follow the structure of a toxic derived from a living organism

How quickly a chemical produces acute and other effects depends on what?

Site and route of exposure

Toxicologist

A scientist who investigates in living organisms the adverse effects of chemicals and assess the probability of their occurrence

Dose-Response Relationship

A type of correlative relationship between the characteristics of exposure to a chemical and the spectrum of effects caused by the chemical

What can the effects be when an organism is exposed to 2 or more chemicals?

Additive Synergistic Antagonistic Coalitive Potentiation

Explain Systemic Effects of exposure to a chemical

Adverse effects associated with generalized distribution of the chemical through the body by the bloodstream into internal organs

What does an individual's response to a toxic exposure depened on?

Age, sex, race, health status, genetics, use of medications, pregnancy status

What are the basic assumptions of toxicology?

All substances are poisons The right dose differentiates a poison from a remedy

Dose

Amount of a substance administered at one time

Chemical Allergy

An immunologically mediated adverse reaction to a chemical resulting from previous sensitization to that chemical or to a structurally similar one

Poison

Any agent capable of producing a deleterious response in a biological system

Explain Target Organ Effects of exposure to a chemical

Some chemicals may confine their effects to a specific organ

What are characteristics of organic toxins?

Carbon-containing, frequently made up of large molecules, capable of being synthesized

What information is a Dose-Response Relationship used to gather?

Causal association between a toxin and a biological effect Minimum dosage needed to produce a biological effect Rate of accumulation of harmful effects

Xenobiotics

Chemical substances that are foreign to the biological system and include chemicals that can produce developmental toxicity

What route of exposure is typically the slowest response to an acute of another effect?

Contact with the skin

Explain Local Effects of exposure to a chemical

Damage at the site where a chemical first comes into contact with the body

Spectrum of Toxic Dose

Describes the toxicity or hazards that are related to exposure to a particular chemical

What route of exposure is typically the fastest response to an acute of another effect?

Direct injection into the blood stream

What are the 3 most frequent sites of exposure to environmental chemicals?

Gastrointestinal tract Respiratory system Skin

Chemical Idiosyncrasy

Genetic predisposition where one either has extreme sensitivity to low doses of a chemical or insensitivity to high doses

What are the 4 general steps of risk assessment?

Hazard ID Dose-Response assessment Exposure assessment Risk charcterization

What does Environmental Toxicology examine?

How environmental exposures to chemical pollutants may present risks to biological organisms (particularly animals, birds, and fish)

Direct Effect of Toxic Exposure

Immediate impact upon the cells and tissues of the body or upon specific target organs

How are the individual and population dose-response curves different?

Individual dose-response curve is graded Population dose-response curve is S-shaped and is also a cumulative percentage response curve

What are the 4 most frequent routes of exposure corresponding to the 3 sites of exposure?

Ingestion Injection into the bloodstream Contact with the surface of the skin Inhalation

What does the nature of a toxic effect depend on?

Innate toxicity of the chemical Concentration Route and site of exposure Personal sensitivity

What are the most common organs to experience Target Organ Effects of exposure to a chemical

Liver, lungs, heart, kidneys, brain, reproductive system, nervous system

What are the 3 types of direct adverse effects of exposure to chemicals?

Local Effects Systemic Effects Target Organ Effects

Dose-Response Assessment

The measurement of the relationship between the amount of exposure and the occurrence of the unwanted health effects

Threshold of a Dose-Response Curve

Lowest dose at which a particular response may occur

What is an example of an indirect toxic effect

Methanol is indirectly toxic through the action of the liver, which coverts to formaldehyde

What does the class of Xenobiotics include

Naturally occurring compounds, drugs, environmental agents, carcinogens, insecticides

What are the 2 types of Dose-Response curves?

One for the response of an individual to a chemical One for the population

Toxin

Organic substance made by living organisms including reptiles, insects, plants and microorganisms

What are examples of hazardous chemicals and other agents that impact human reproduction negatively?

Pesticides, drugs, heavy metals and hormones

Exposure

Proximity and/or contact with a source of a disease agent in such a manner that effective transmission of the agent or harmful effects of the agent may occur

Toxic Agent

Refers very generally to a material or factor that can be harmful to biological systems

Fields of toxicology

Regulatory toxicology Forensic toxicology Clinical toxicology

Developmental Toxicology

Researches the effects of natural and man-made chemicals on prenatal development

What is the concentration and toxicity of a chemical affected by?

Route of entry into the blood Received dose of the chemical Duration of exposure Personal sensitivity Prevalence of other chemicals

Coalitive

Several agents that have no known toxic effects interact to produce a toxic effect

Organic Toxin

Substance that is originally taken from living organisms that is toxic

Additive

The combination of 2 chemicals produces an effect that is equal to their individual effects added together

Synergism

The combined effect of exposures to 2 or more chemicals is greater than the sum of their individual effects

Toxicity

The degree to which something is poisonous

LD50 (Lethal Dose 50)

The dosage (mg/kg) causing death in 50% of exposed animals

Hazard

The inherent capability of an agent or a situation to have an adverse effect

Risk Assessment

The process of determining risks to health attributable to environmental or other hazards

Environmental Toxicology

The study of how ecological systems-their structure, dynamics, function, etc.- are affected by pollutants

Toxicology

The study of the adverse effects of chemicals on living organisms

What do Toxicologists take into account?

The total dose How often each individual dose occurs The time period during which the dosing occurs

Target Organ Toxins

Those toxins that affect specific parts of the body

Systemic Toxins

Those toxins that affect the entire body or multiple organ systems

What is the use of LD50?

To compare toxicities of chemicals and to describe toxic effects

Toxicants

Toxic substances that are man-made or result from human (anthropogenic) activity

T/F: Virtually all known chemicals have the capacity to produce toxic effects

True

Dose-Response Curve

Type of graph that is used to describe the effect of exposure to a chemical or toxic substance upon an organism

Potentiation

When one chemical that is not toxic causes another chemical to become more toxic