Pcbs: Not Just A Local Problem

Polychlorinated Biphenyls

a. Basic Chemical Structure and Makeup:

Polychlorinated Biphenyls (PCBs) are man made chemicals whose birth came in the early Twentieth Century. They are not found anywhere in nature, and are classified by chemists as chlorinated oils with a low degree of reactivity.

Regarding the chemical structural of PCBs, two distinct groups of this compound can be established: Basic PCB Structure and Toxic PCB Structure. The basic structure is comprised of a biphenyl (two benzene rings with a carbon to carbon bond) with a varying number of bonded chlorine molecules along the outside of the biphenyl structure. The toxicity of this compound, however, is dependent upon how many chlorine molecules are present on the biphenyl structure. Thus the more chlorine molecules contained within a PCB, the more toxic the actual compound is. (See figure I.I)

Toxicity is not the only chemical aspect whose scale and extent is dependent upon the number of chlorine molecules present within the compound. Among other characteristics, biodegradability is also connected with to the amount of chlorination of a particular PCB. "The higher the chlorine content of a PCB, the less the biodegradability. The lack of degradability of PCB compounds result in bioaccumulation of PCBs in the environment."

The name of each PCB is also dependent upon how many chlorine molecules it contains. The nature of the biphenyl structure allows a single attachment to each carbon, meaning that there are ten potential positions for chlorine substitution. The United States Environmental Protection Agency (EPA) explains that: "Species with a single chlorine substitute are called Ð''Monochlorobiphenyl.' Species with two chlorines are called Ð''Dichlorobiphenyl', and those with three through ten chlorines, in order, are called: Ð''Tri...', Ð''Tetra...', Ð''Penta...', Ð''Hexa...', Ð''Hepta...', Ð''Octa...', Ð''Nona...', and Ð''Decachlorobiphenyl.'"

Along with this, each specific PCB is given a four digit code in order to easily classify its chemical makeup and origin. The first two digits are typically twelve, indicating the number of carbon molecules in their structures. The second pair of digits, however, indicates the average percent weight of chlorine. 1242, 1245, and 1260, for example, are all code designations for specific PCB compounds.

b. Functions and Uses:

Polychlorinated Biphenyls first appeared in America in 1929, after they were introduced to the economy by the Monsanto Corp. (the first and only company to manufacture PCBs). Not only was the new chemical inflammable, but had high electrical resistance, positive insulation qualities, and such resistance to fire that they were actually required by fire code.

Aside from the many constructive and chemical aspects of PCBs, they had several uses as well. Roberta C. Barbalace explains:

Uses for PCBs quickly expanded to include hydraulic fluids, casting wax, carbonless carbon paper, compressors, heat transfers systems, plasticizers, pigments, adhesives, liquid cooled electric motors, fluorescent light ballasts, and the list goes on.

The PCBs manufacturing desirability was mostly attributed to their high thermal and chemical resistance, which meant that they didn't break down when exposed to heat or chemical treatment.

After many negative health effects were observed on factory workers by corporate superiors in the 1940's, the US Congress outlawed PCB manufacturing, sale, and distribution. However, this law was excluded to companies who manufactured PCBs in "totally disclosed areas."

c. Effects and Consequential Hazards to Health and the Environment

Between the 1940s and 1976, the General Electric Corp. polluted the local Hudson River with roughly 1.3 million pounds of PCBs. The reckless contamination ruined the local fishing industries, yet Pres. Ronald Reagan stalled the initiation of dredging the river in the early 1980's. In 2002, however, the EPA re-issued its proposal for the de-contamination of the Hudson River. The imitative led the association to re-open other environmental cases involving PCBs and their effects on human health and the environment.

Regarding the hazards of PCBs to human health, the following conditions have been traced back to this dangerous chemical compound:

Ð'* Liver Disease

Ð'* Serious damage to the Endocrine, immune, and nervous System

Ð'* Hormones and Enzymes (as well as chloracne)

Ð'* Birth Defects

The effects of PCBs on the environment are equally startling. In the rivers and lakes, PCBs attach to sediments, remain buried for a long period of time, and are eventually released into the air. From there, the compound can build up in animals, nestling into fatty tissues of land and aquatic animals. While the latter is more prone to death from PCBs in the water, biomagnification will usually occur on land because of the dangerous chemical compound. In addition, marine biomes are reportedly the most susceptible to contamination. In seawater in industrial areas, for instance, were observed to be at least 100 times higher than further off-shore.

Aside from biomes, however, are the effects of Polychlorinated Biphenyls on the air and atmosphere.

Since the early 1980s, there has been a slight but continuous decrease in the levels of PCBs in air observed in urban, rural, and coastal areas. By the early 90s, PCB concentrations in rainwater from continental areas had dropped to one quarter or less of their levels in the late 70s, with values decreasing from 20 to 5 ng/litre [0.02-0.005 ng/m3] in rural areas and from 50 to 10 ng/litre [0.05-0.01 ng/m3] in cities.

Indoors, however, PCB levels are ten times higher than in the adjacent outdoor areas. This is mostly due to outdated home and manufacturing devices whose origin lies in the era of mass PBC manufacturing in the United States and Canada.

The General Electric Corp.

a. Background in Regards to PCBs

The General Electric Corp., one of the largest American-made corporations on the planet, was founded in 1892. Since the start of mass PCB manufacturing across