Question

Complete the following with concise answers:

1. Explain the dominant exposure pathway for polychlorinated biphenyls (PCBs) in the environment for most human exposure.
2. Name three health outcomes linked with chronic PCB exposure.
3. Chlorofluorocarbons are synthetic organic chemicals but their hazard is distinct from the other chemicals covered in class. Explain this distinction in terms of chemical stability and health effects.
4. Generally speaking, blood lead levels in the US population has been declining over the past few decades. Give two reasons that can explain this.
5. Name two reasons why people are concerned about the potential risks of nanomaterials

Answer 1

(a) Food is the main source of exposure to Polychlorinated biphenyls for the general population. Exposure of PCBs occurs in humans primarily by ingesting high-fat foods such as eggs, dairy products, and animal fats and some fish and wildlife. The resistance of these compounds to biodegradation causes them to become more concentrated as they move upward through the food chain from the bottom-feeding organisms.

health outcomes-

• Increased levels of some liver enzymes, with possible hepatic damage,
• Chloracne and related dermal lesions
• Respiratory problems
• carcinogenesis

(b) CFCs are chemically stable since they are not having any single hydrogen. Humans can come in contact with CFCs through ingestion or skin contact. After dermal interaction with CFCs, some people might have skin irritation, or exposure to pressurized CFCs, such as that from a refrigerant leak, can cause frostbite on the skin. Direct skin exposure to CFCs has not been linked to cancer. Ingestion of CFCs can cause nausea, vomiting, diarrhea or other upset to the digestive tract.

CFC reaches in atmosphere breakdown by UV rays cause a chain resolution in the ozone layer to cause its depletion.

(c) the major cause of the observed decline in blood lead levels is most likely

• the removal of 99.8% of lead from gasoline
• the removal of lead from soldered cans

(d)  The ability of nanoparticles to spread within the body, as well as their solubility, are the key factors for risk,

For humans, inhalation is the most frequent route of access, and therefore the process of aggregation of the nanoparticles in the inhaled air has to be taken into account. The inhaled nanoparticles can reach the blood and may reach other target sites such as the liver, heart or blood cells and accumulate.Nanoparticles may translocate through membranes. There is little evidence for an intact cellular or sub-cellular protection mechanism.