TOXICOLOGY – The study of poisons

Materia Medica – poisons classification - Dioscorides Court of Nero, 50 AD “The dose makes the poison” - Paracelsus 16 th 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 NormalNormal 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 Effects A. Immune suppression 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 Effects Continued C. Carcinogenic Uncontrolled growth of genetically-controlled cells Multi-stage theory Initiation Promotion Progression D. Tetratogenesis – changes in embryos

Effects on Life Processes A. Exposure of an individual to a toxic substance may alter one or more basic life processes, including: 1. Irritability – ability to respond to stimulus 2. Conductivity – nerve impulses 3. Contractility – ability to change form by shortening 4. Metabolism 5. Integration – ability to coordinate activities by acceleration or deceleration or activities 6. Adaptation 7. Reproduction – ability to repair and reproduce

Effects on Life Processes Continued 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 Management Continued 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 Databases on toxicology, hazardous chemicals, environmental health, and toxic releases Toxicology tutorial Amer. Assn. of Poison Control Centers OSU Community Outreach and Education Program Classroom activities and labs - toxicology