Lecture 3 Flashcards
Toxicology
Because of the quantity and variety of chemicals used by the chemical process industries, chemical engineers must be knowledgeable about:
the way toxicants enter biological organisms
the way toxicants are eliminated from biological organisms
the effect of toxicants on biological organisms, and
methods to prevent or reduce the entry of toxicants into biological organisms
Fundamental Principle of Toxicology:
There are no harmless substances, only harmless ways of using substances.
qualitative and quantitative study of the adverse effects of toxicants on biological organisms
Toxicology
can be a chemical or physical agent, including dusts, fibers, noise, and radiation.
Toxicant
property of a toxicant describing it effect on biological organism
Toxicity
likelihood of damage to biological organism based on exposure resulting from transport and other physical factors of usage.
Toxic Hazard
Routes of Entry
Ingestion, Inhalation, Absorption/Injection
Routes of entry: Ingestion
through the mouth into the stomach
Routes of entry: Inhalation
through mouth/nose into lungs
Route of Entry: Absorption/Injection
through skin
Plays the most significant role in toxicants entering the body through ingestion
gastrointestinal tract
plays a role in absorption and injection routes of entry
skin
for toxicants entering the body through inhalation
respiratory system
rule of thumb for dust particles:
the smaller the particles, the farther they penetrate into the respiratory system
toxicants are eliminated by the following routes:
Excretion
Detoxification
Storage
Minor routes of toxicant exit:
skin(sweat), hair, and nails
toxicant eliminated through kidneys, liver, lungs, or other organs
excretion
toxicants are eliminated by changing the chemical into something less harmful by biotransformation, usually processed by the liver but can also occur in the blood, intestinal tract wall, skin, kidneys, and other organs.
Detoxification
toxicants are eliminated by depositing of chemical agent in the fatty tissue, bones, blood, liver, and kidney
storage
Toxic chemicals disrupt the normal function of the body. effects can be:
local - at the site of the exposure
systemic - affecting the entire body or target organs
medical examinations: pre-employment and periodic
to determine whether exposures have occurred before substantial symptoms appear
tests that may be conducted:
spirometry - respiratory problems
electroencephalogram (EEG) or other psychological tests - for nervous system disorders
physical exam - changes in skin texture, pigmentation, hair or nail appearance
blood counts - measure hemoglobin, RBC/WBC, platelet and other parameters needed
kidney function test - creatinine content of urine
liver function test - through blood and urine
Factors in toxicological studies
- toxicant (chemical composition and physical state)
- target or test organism (simplee single cell to higher animals)
- effect or response to be monitored
- dose range (depend on method delivery)
- period of the test
to quantify the effects of the suspect toxicant on a target organism
toxicological studies
Type of toxicities by length of time:
acute toxicity
chronic toxicity
effect of a single exposure or series of exposure in a short period of time. basis for most toxicological studies.
acute toxicity
effect of multiple exposures occurring over a long period of time
chronic toxicity
if several chemical are involved, the toxicants might interact:
additively
synergistically
potentiately
antagonistically
combined effect is the sum of the individual effects
additively
combined effect is more than the individual effects
synergistically
presence of one increase the effect of the other
potentiately
both counteract each other
antagonistically
Classifications of dose:
- effective dose
- lethal dose
- toxic dose
toxicant dose at c=which the response is minor and reversible
effective dose (ED)
toxicant dose poses a risk of death or lethality
lethal dose (LD)
used for gases (toxicant dose0
lethal concentration
dose where the response is toxic, not lethal but causing irreversible damage
toxic dose (TD)
established by the American Conference of Governmental Industrial Hygienists (ACGIH)
Threshold Limit Values (TLV)
three types of TLV
TLV-TWA
TLV-STEL
TLV-C
time weighted average for a normal 8-hr workday or 40-hr work week
TLV-TWA
short term exposure limit; max. concentration to which workers can be exposed for a period of up to 15 min continuously without suffering intolerable irritation, chronic or irreversible tissue change, narcosis of sufficient degree to increase accident proneness
TLV-STEL
ceiling limit
TLV-C
Threshold dose defined by OSHA
permissible Exposure Limit (PEL)
dose or quantity where exposure must be avoided under any circumstances
Immediate Danger to Life and Death (IDLH)
for some toxicants, particularly carcinogens, exposures at any level are not permitted
Zero Threshold
