Department of Chemistry CHEM1020 General Chemistry *********************************************** Instructor: Dr. Hong Zhang Foster Hall, Room 221 Tel:

CHEM1020/General Chemistry _________________________________________ Chapter 20. (L31)-Chemical Toxicology Today’s Outline … Chemical carcinogens carcinogens and cancers what causes cancers how cancers develop chemical carcinogens anticarcinogens … Testing for carcinogens the Ames test: bacteria screening animal testing epidemiological 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 (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 chemical s are carcinogenic Examples: Polycyclic aromatic hydrocarbon (PAHs) 3,4,-benzpyrene, notorious one PAHs 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: bacter ial 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: bacter ial 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 subjects high doses with less animal subjects controls 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) + 2H 2 O(l) = 2NaOH(aq) + H 2 (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 2C 6 H 14 (l) + O 2 (g) = 12CO 2 (g) + 14H 2 O(g) Accident: Louisville, KT Other 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)  Fe 2+ + H 2 (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 , pp.664) Bioremediation Plants: phytoremediation Microbes: microbial remediation Genetic engineering and remediation

Chapter 20. (L31)-Chemical Toxicology Quiz Time TBA