toxicology – the study of poisons. materia medica – poisons classification - dioscorides court...

TOXICOLOGY – The study of poisons

Materia Medica – poisons classification- DioscoridesCourt of Nero, 50 AD

“The dose makes the poison”- Paracelsus16th century German

physician

Scope of the Problem Reagents can represent a toxicity

hazard to students and instructor. Protection of students and staff is

important. Most common sources of contamination

Pipetting by mouth Eating with contaminated hands Drinking from contaminated containers Applying contaminated make-up

EFFECTS OF TOXIC CHEMICALS

Structural Differences are very important:

For example, two closely related PCB’s

Basic Considerations Dose

Length of Exposure

Organs or systems on which the chemicals have an effect

Hypersensitive

Normal

Normal

Hyposensitive

Dose-Response Relationships

Dose Response Relationship Dose make the poison Dose units provide toxicity

measurements Major response terms for toxic or

lethal: Toxic concentration: TC Toxic dosage: TD Lethal concentration: LC Lethal dosage: LD

Toxicity may be different in different species:

Most Common Routes of Entry

Oral Gastrointestinal tract exposure

Inhalation Respiratory tract exposure

Pericutaneous Through the skin, a dermal or

epidermal exposure

Major Sites of Exposure, Metabolism, Storage and Excretion

Local and Systemic Effects Local Effect

Occurs directly where the chemical contacts the body

Systemic Effect Caused when a toxic reagent is absorbed

and circulated by the blood to systems and organs that can be effected by the toxin

Effects may be lessened by the body’s ability to detoxify and eliminate the toxin

Acute and Chronic Effects

A. Acute exposure Single or short-term exposure May have sudden onset of affect and a

short duration Some short term exposure may cause:

Permanent adverse effects Delayed effects Chronic effects

Acute and Chronic Effects Continued

B. Chronic exposure and effects Repeated or prolonged exposure to

low concentrations of toxic chemicals Chronic effects are:

Of long duration Frequently recurring Slowly progressing in seriousness

c. Similar exposure to some toxins will have effects that stop when exposure stops

General Classes of EffectsA. Immune suppression

t-cells t-cells

B. Central nervous system effect CNS is most sensitive to adverse changes in brain

function or nerve conditions Drugs: designer drugs, phenobarbitol, narcotics

Solvents: toluene, styrene, xylene, methyl ethyl ketone

General Classes of EffectsContinued

C. Carcinogenic Uncontrolled growth of genetically-

controlled cells Multi-stage theory

Initiation Promotion Progression

D. Tetratogenesis – changes in embryos

Effects on Life ProcessesA. Exposure of an individual to a toxic

substance may alter one or more basic life processes, including:

1. Irritability – ability to respond to stimulus2. Conductivity – nerve impulses3. Contractility – ability to change form by

shortening4. Metabolism5. Integration – ability to coordinate activities by

acceleration or deceleration or activities6. Adaptation7. Reproduction – ability to repair and reproduce

Effects on Life ProcessesContinued

B. System toxic effects are often first recognized as shift in physiological or behavioral patterns

Shift may be subtle or dramatic

Toxicology Management

A. Risk vs. Benefit Least-toxic reagents Alternate procedures Simulations

B. Voluntary vs. Involuntary Risk Instructor Student Experienced research scientist

Toxicology ManagementContinued

C. Setting Standards OSHA

Chemical hygiene plan “Right to Know” law Disposal regulations

NIOSH

D. Sensitive Sub-Populations Pregnant females Allergic reactors

Toxicology Databases Toxnet – National Library of Medicine

http://toxnet.nlm.nih.gov/Databases on toxicology, hazardous chemicals, environmental health, and toxic releases

Toxicology tutorial

Amer. Assn. of Poison Control Centershttp://www.aapcc.org/

OSU Community Outreach and Education ProgramClassroom activities and labs - toxicology

http://www.hydroville.org