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Department of Chemistry
CHEM1020 General Chemistry***********************************************
Instructor: Dr. Hong ZhangFoster Hall, Room 221
Tel: 931-6325
Email: [email protected]
CHEM1020/General Chemistry_________________________________________
Chapter 20. (L31)-Chemical Toxicology
• Today’s Outline
…Chemical carcinogens
carcinogens and cancers
what causes cancershow cancers developchemical carcinogensanticarcinogens
…Testing for carcinogens
the Ames test: bacteria screening
animal testingepidemiological studies
Chapter 20. (L31)-Chemical Toxicology
• Carcinogen…Carcinogen: something that causes the growth of tumors.…A tumor is an abnormal growth of new tissue and can be either benign or malignant.
Benign tumors grow slowly, often regress at the same time, do not invade neighboring tissues.
Malignant tumors, cancers, can grow slowly or rapidly, but their growth is generally irreversible, which invades and destroy neighboring tissues.
Cancer is a complicated disease.
Chapter 20. (L31)-Chemical Toxicology
• What causes cancer…Major causes
genetic
environmental
natural carcinogens
anthropogenic (pollution, such as chemical carcinogens)
life-style or behavior
see Fig. 20.7 (pp.657)
Chapter 20. (L31)-Chemical Toxicology
• How cancers develop…Development mechanisms
modifying DNA
gene activation (oncogenes)
other mechanisms under investigation
Chapter 20. (L31)-Chemical Toxicology
• Chemical carcinogens…A variety of chemicals are carcinogenic
Examples:Polycyclic aromatic hydrocarbon (PAHs)
3,4,-benzpyrene, notorious onePAHs come from incomplete burning
of organic compounds e.g., charcoal-grilled meats, cigarette
smoke, automobile exhaust, coffee, brunt sugar, etc.
Chapter 20. (L31)-Chemical Toxicology
• Chemical carcinogens…A variety of chemicals are carcinogenic
Examples:
Aromatic amines
β-naphthylamine
benzidine
in dye industries
Chapter 20. (L31)-Chemical Toxicology
• Chemical carcinogens…A variety of chemicals are carcinogenic
Examples:
Non-aromatic amines
dimethylnitrosamine
vinyl chloride
Heterocyclic rings containing N and O
Chapter 20. (L31)-Chemical Toxicology
• Anticarcinogens…Yin and Yang
anticarcinogens:
antioxidant vitamins
butylated hydroxytoluene (BHT), a food addictive
there are more we just don’t know yet
Chapter 20. (L31)-Chemical Toxicology
• Tests for carcinogens…Question: how do we know if something is carcinogenic?
We get to know or guess by running some tests (not on human subjects)
Thus, we have to know something about possible carcinogens by these tests conducted not directly on human subjects
Chapter 20. (L31)-Chemical Toxicology
• Tests for carcinogens…The Ames test: bacterial screening
A simple lab procedure done in a petri dish. The test is based on the assumption that
most carcinogens are also mutagens. The Ames test was developed by Bruce N.
Ames of UC Berkeley A special strain of bacteria called
Salmonella that have been modified so that they require histidine as an essential amino acid.
Chapter 20. (L31)-Chemical Toxicology
• Tests for carcinogens…The Ames test: bacterial screening
The modified bacteria is put in a petri dish with all nutrients needed except for histidine, plus a potential carcinogen to be tested.
The bacteria can only grow if they can mutate to another type that does not require histidine as the essential amino acid.
If the growth of the bacteria is observed, then this suggests that the substance tested could potentially be a carcinogen.
Chapter 20. (L31)-Chemical Toxicology
• Tests for carcinogens…Animal testing
The suspected chemicals can be tested on animals. Approaches:
low doses with many animal subjectshigh doses with less animal subjectscontrols
If more occurrences of cancers are observed on the animals treated with the chemical than on the controls, then the chemical is potentially carcinogenic. …Shortcomings of animal tests
Chapter 20. (L31)-Chemical Toxicology
• Tests for carcinogens…Epidemiological studies
The best evidence that a substance may cause cancer in human beings comes from epidemiological studies.
Using biostatistical tools to analyze epidemiological data and identify the possible correlation between certain cancer and a suspected carcinogen.
Not necessarily cause-effect relationship, but the correlation is still useful and can server as a guideline.
Chapter 20. (L31)-Chemical Toxicology
• Hazardous wastes…Classification of hazardous wastes
Four types:
reactive
flammable
toxic
corrosive
Chapter 20. (L31)-Chemical Toxicology
• Hazardous wastes…Classification of hazardous wastes
Four types:
A reactive waste tends to react spontaneously or vigorously with air or water.
2Na(s) + 2H2O(l) = 2NaOH(aq) + H2(g)
Chapter 20. (L31)-Chemical Toxicology
• Hazardous wastes…Classification of hazardous wastes
Four types:
A flammable waste burns readily on ignition, presenting a fire hazard
Example: Hexane, a hydrocarbon solvent
2C6H14(l) + O2(g) = 12CO2(g) + 14H2O(g)
Accident: Louisville, KTOther examples: gasoline, fuels
Chapter 20. (L31)-Chemical Toxicology
• Hazardous wastes…Classification of hazardous wastes
Four types:A toxic waste contains or releases toxic
substances in quantities sufficient to pose a hazard to human health or to the environment.
PCB, Hg, heavy metals, and on and on.
Chapter 20. (L31)-Chemical Toxicology
• Hazardous wastes…Classification of hazardous wastes
Four types:A corrosive waste is one that requires special
containers because it corrodes conventional container material.
Acid cannot be stored in steel drums
Fe(s) + 2H+(aq) Fe2+ + H2(g)Strong base solution cannot be stored in glass
containers. Reactions between the substance of concern and
the container material.
Chapter 20. (L31)-Chemical Toxicology
• Green chemistry…Production of chemicals that are not or less toxic or hazardous or can naturally disappear to non-hazardous substances in the environment.
A very active field.
Chapter 20. (L31)-Chemical Toxicology
• Waste treatment…Incineration
A technology to treat organic wastes at 1260 ºC (Fig. 20.10, pp.664)
Bioremediation
Plants: phytoremediation
Microbes: microbial remediation
Genetic engineering and remediation
Chapter 20. (L31)-Chemical Toxicology
Quiz TimeTBA