Applied Human Toxicology Flashcards
Animals - Why are they different?
- Animals are inbred, genetically identical
- Doses can be higher than humans
- Can easily study cellular effects, pathology
- Can evaluate large numbers of animals
- Results more defined and interpretable
- Fewer confounding factors
- Lifestyle, complex exposures, genetics
Differences with humans?
- Wide genetic variation
- Exposures lower, less defined, often mixed**
- Life style variables
- Exercise, smoking, alcohol, diet, etc) - Lack of inbred control groups
- Limited acceptable protocols
Animal Tox Methods?
Route of exposure Type of exposure In vivo - Expose animal** Evaluate whole animal response Evaluate cellular changes In vitro - Cellular effects**
Routes of exposure - Animals?
Injection, IP and IM Oral gavage Inhalation Dermal Food Drinking water Injection and oral gavage relevant for humans**
Types of exposure - Animals?
Acute - irritant to eye, skin, sensitization Acute - LD 50 Subacute - range-finding, days Subchronic - days to weeks Chronic - months to years Acute, subacute relate to humans**
In vivo animal testing?
Expose and Evaluate Whole Animal End Points
Pathology End Points
Other Cellular End Points
In vitro animal testing?
Cellular Level Studies
Human Subject Committees
- Must have lay representation**
- Informed consent
- Medical monitoring of project
- Selection criteria of exposed and controls
- Communicate results to subject and doctor
- Deals with real and perceived issues impacting the subject
- Who gets the results?
Ethics of Human Exposure
Studies
- Should humans be exposed to toxics?
What about children? - What are health effects of exposure?
- Are there hyper-responsive subjects?
- Response plan for possible acute effects?
- What legal protection does researcher have?
- Are alternatives available?
Routes of exposure - Humans?
1. Inhalation - common in workplace Nasopharyngeal Tracheobronchial Pulmonary - Alveoli 2. Percutaneous - occup and environmental Stratum corneum Epidermis, dermis
Oral Ingestion - Humans
What Foods & water How Hand to mouth contact (demonstrate) Special problems with children Mechanism Solubility and pH dependent Remember Henderson-Hasselbalch equation?
Types of human studies?
- Case reports
- Controlled laboratory testing or challenge tests
- Workplace exposure studies
- Epidemiology studies
Case Reports
- Usually involve one patient
- Lack of information on exposure
- Many confounding factors
- Not research but anecdotal
- Not generalizeable
Controlled Laboratory Exposure
- Need controls and exposed subjects
- Expensive, small number of subjects
- Low level exposures - uncertain effects
- Limited to acute or short-term exposures
- Do not reflect “real world” exposures
- Analysis and reporting differences from
different studies
- Meta analysis
Other issues in human studies?
- Workload impacts inhalation exposure
- Route of exposure often mixed
- Clothing and temperature impact dermal
exposure - Difficulties in conducting 8-hr exposures
- Bathroom and food breaks
- Specimen collection
Occupational or Environmental
Field Studies- Assessments
Confounding factors, mixed exposures Widely variable exposures during work day Combined job and environment exposures Second job exposures or hobbies No control for life-style variables Controls - matched or own control?
Epidemiology Studies - Outcomes
What was the cause?
Need large population and controls
Multiple exposures - work & environmental
Exposure assessment often lacking
Genetic predisposition, susceptibility
Life style variables, the gray zone
Cannot often isolate the cause to a single agent
Epidemiology studies - Examples
Benzene exposure (retrospective) Leukemia incidence related to past exposure What dose causes leukemia? Aniline and o-tolidine in tire making Excess of bladder cancer Biomarkers of aniline and o-tolidine identified NIOSH alert What was the exposure?
Other Types of Exposure Endpoints
Cytogenetic end points in blood Chromosomal abberations Sister chromatid exchange Micronuclei Metabolism studies - examples Benzene - field PAHs - field Chlorobenzene - experimental
Comparison of human Epi versus animal exposure studies (Table 34-7)
Toxicant exposure, species consideration, analytical challenges
Examples of Exposure Studies
Incident related studies Toxicokinetic studies - examples MBOCA - Accident Health effects studies -examples Arsenical keratosis – field Hiroshima studies In vitro studies in humans Lypmocytes, tissue cultures, DNA cross-linking