This news item was created by students Nick Bauer, Christine Brenneke, Sadaf Ejaz, Krista Fohey and Sharon Teoh as part of their Chemistry 212 Collaborative Group Activities in WS00 under the guidance of Prof. Rainer Glaser.

Glaser's "Chemistry is in the News"
To Accompany Wade Organic Chemistry 4/e.
Chapter 16. Aromatic Compounds.


For each of the following questions, please refer to the following article:

EVERYDAY EXPOSURE TO TOXIC POLLUTANTS
By Wayne R. Ott and John W. Roberts (Scientific American, February 1998)


Editorial Comments

Prolonged exposure to many chemicals found in household products pose numerous health risks. Among these carcinogenic compounds are benzene and derivatives of benzene such as dichlorobenzene and benzo[a]pyrene. Benzene is found in gasoline, glue, paint, cleaning products and cigarettes. The harmful effects of benzene cause a reduction in the strength of the immune system leading to a greater susceptibility to cancer like leukemia and other health problems such as anemia and internal bleeding. High levels of exposure to these compounds result in death. DDT (dichlorophenyl-trichloroethane) is another derivative of benzene. In the 1940's, this insecticide was discovered to cause insect resistance and proved to be highly toxic in animals. Although banned in the United States, DDT is often found in various parts of the world as an efficient insecticide.

Polycyclic aromatic hydrocarbons are reactive chemicals that can cause many health problems. Due to the growing awareness of the effects of pollutants on the environment, the government regulates many of these toxic chemicals in order to reduce the amount of pollutants outdoors. But most people do not give a second thought to the amount of chemicals that could be in their homes. They will clean their home and not even worry. Unfortunately, once many of these polyaromatic hydrocarbons are into the home, they never leave. This leads to a build up of compounds such as benzo[a]pyrene and benzo[a]anthracene. Both of these are carcinogens. It is scary to think that these compounds can get into the carpet or a person's favorite lazyboy.

The Clean Air Act first went into effect in 1970 in hopes of decreasing the release of dangerous chemicals and pollutants in the air. One of the main topics that the Clean Air Act deals with is the regulation of air pollution. The latest amendment added to the Clean Air Act was in 1990. This amendment gave enforcement powers to the Environmental Protection Agency (EPA). The EPA grants permit fees to companies that allow pollutants to enter the air. The Clean Air Act also sets up deadlines in which companies must reduce air pollution.

By avoiding the use of some household products such as air fresheners, aerosol sprays and cigarettes, the effects of these harmful volatile organic chemicals can be reduced in the home.

Pertinent Text References
Chapter 16. Aromatic Compounds



Questions

Question 1: What products would you limit the use of in order to decrease indoor pollution?

Answer: Tetrachloroethylene is used for dry-clean clothes. Paradichlorobenzene is found in mothballs. PAH's are found in coal tar and are very carcinogenic.

Question 2: Look up the structure of DDT (dichlorodiphenyltrichloroethane). How is DDT synthesized? What properties of DDT make it toxic and a possible carcinogen for human?

Answer: The DDT structure can be found using the Chemfinder program. The synthesis of DDT is available on the web. Although DDT has low toxicity, it is also fat-soluble and can accumulate in the body and reach toxic levels. The half-life for DDT is 8 years therefore it is metabolized slowly in humans and constant exposure to DDT is highly toxic.

Question 3: What is P-dichlorobenzene (PDB or p-DCB)? How does exposure to it endangers us?

Answer: The structure of PDB can be found using the Chemfinder program. PDB is used as a fumigant for insect and is used for small animal control. It is widely used in the production of low-pressure aerosols because of its insecticide action and its properties as a solvent. However, PDB is toxic. Below is a link related to the use of PDB, how we could be exposed to PDB, its toxicity and how it affects our health. The structure of PDB is found on the web. .

Question 4: How are polycyclic aromatic hydrocarbons formed? Benzo[a]anthracene is a carcinogenic polycyclic aromatic hydrocarbon. Draw the structure of this molecule using the Chemfinder program. Benzo[a]anthracene has been found to cause brain tumors in lab animals. Name three other PAH's that have caused the same effects. Another compound, benzo[a]pyrene has shown other adverse effects. Name a few of these effects and give the structure of this compound.

Answer: The structure of benzo[a]anthracene and benzo[a]pyrene can be found using the Chemfinder. PAHÕs occur in nature and are also formed when organic compounds are not burned completely. There are many different PAHÕs and three examples are acenaphthene, anthracene and chrysene. Some possible side effects from benzo[a]pyrene are birth defects, decrease in body weight and cancer. All this information is provided on the following website: www.atsdr.cdc.gov/ToxProfiles/phs9020.html .

Question 5: When and why was the Clean Air Act put into effect? What are some of the chemicals that are regulated in the Clean Air Act?

Answer: The Clean Air act came into effect in 1970 and was created to reduce the emissions of air pollutants. Chemicals regulated under the Clean Air Act are ozone, carbon monoxide, sulfur dioxide and nitrous oxide.

Question 6: There are over 40,000 chemicals in tobacco smoke including benzene and pyridine. Draw the Lewis structure of pyridine.

Answer: The Lewis structure is found on page 709 of the Wade Organic Chemistry book.

Question 7: How many people die annually from second-hand smoke?

Answer: Every year, 3000 people die from second hand smoke.