Toxicology an Abandoned Industrial Park

Toxicology

An abandoned industrial park sits as a potentially toxic wasteland. The two now-defunct companies that had been using the site for heavy manufacturing have left a mess for others to clean up. For sixty years, these two companies manufactured goods that resulted in the production of a number of different waste products. One of the things we do know is that two culprit companies had been producing polychlorinated biphenyls (PCBs), chromium waste, acrylamide, and tolulene diisocyanate (TDI). Those waste products were not disposed of properly, and now we must remedy the situation to ensure that the site and its surrounding areas are safe.

Moreover, we need to perform a thorough toxicology analysis to ensure that groundwater sources are uncontaminated and safe. As many as one hundred drums, which are unmarked and therefore might all contain toxic waste, have been buried on the site. Furthermore, most of those chemical-filled drums are deteriorating. Rust and cracks are compromising the integrity of the drums, allowing the chemicals inside to pollute at least the air and quite possibly the soil and groundwater as well. In fact, any visitor to the site is struck by the strong stench of industrial chemicals in the air.

One of the greatest concerns with this site is the potential for groundwater contamination. There is one stream that runs through the site, which puts anything downstream from the site in danger. In fact, one mile downstream is a residential area, a source of local drinking water, and a surface water withdrawal point for irrigation as well. The stream that runs through the site also happens to be a fishing stream popular with locals, which raises serious questions of not just the local water quality but also the quality of the fish and any agriculture coming from this area.

The toxicology issues related to this case can be assessed first by identifying the specific hazards, which have already been measured in this case. The hazard identification will be accompanied by a thorough review of the scientific literature related to those specific toxins. The assessment will also include a risk assessment, which will be related to the amount of each toxin present, the type of exposure, the level of exposure, and the potential impact on local communities.

Hazard Identification

The four chemicals that have already been identified on the site include Polychlorinated Biphenyls (PCBs), chromium waste, acrylamide, and tolulene diisocyanate (TDI). Some of these chemicals are known to be so hazardous that they are no longer permitted for use in American manufacturing.

Polychlorinated Biphenyls (PCBs)

PCBs were initially used as industrial coolers and lubricants "because they don't burn easily and are good insulators," (Agency for Toxic Substances and Disease Registry 2001). According to the Agency for Toxic Substances and Disease Registry (2001), there are over 200 types of PCBs, which are all variations of chlorinated hydrocarbon. Of the over 200 PCB, none have natural sources. All PCBs are synthetic chemicals that were once commonly used in "hundreds of industrial and commercial applications including electrical, heat transfer, and hydraulic equipment; as plasticizers in paints, plastics, and rubber products; in pigments, dyes, and carbonless copy paper; and many other industrial applications," (U.S. Environmental Protection Agency 2010). However, PCBs are now phased out due to toxicology.

The chemicals were manufactured from the 1920s until 1979, after which they were banned. However, products manufactured prior to the PCB ban will still contain the chemical. For example, a lot of electrical equipment manufactured before 1979 such as fluorescent lighting fixtures, televisions, refrigerators, transformers, and capacitors may contain PCBs. Other products made before 1979 including the oil used in motors and hydraulic systems; oil-based paint; caulking; thermal insulation material; and floor finishers may also contain PCBs (Agency for Toxic Substances and Disease Registry 2001; EPA 2010).

Proper disposal of PCB-containing materials is crucial for public health. The EPA (2010) points out that PCBs "can still be released into the environment from poorly maintained hazardous waste sites that contain PCBs." Moreover, "illegal or improper dumping of PCB wastes; leaks or releases from electrical transformers containing PCBs; and disposal of PCB-containing consumer products into municipal or other landfills not designed to handle hazardous waste," cause PCBs to enter sources of drinking water (EPA 2010).

The reason why PCBs were banned as early as 1979 is because they are known toxins and possible carcinogens. PCBs are classified officially as a group B2 carcinogen (EPA 2010). Skin conditions, neurobehavioral issues, and immunological problems in children are also linked to exposure to PCBs (Agency for Toxic Substances and Disease Registry 2001).

Fishing in contaminated waters is a major way that PCBs enter into the food chain and are ingested by humans. In fact, after PCBs enter the food chain, toxicity levels in fish may be thousands of times higher than in water," (Agency for Toxic Substances and Disease Registry 2001). This is because the fish that humans eat are relatively high on the food chain, and have already ingested and metabolized the aquatic life containing the harmful chemicals. Drinking well water from PCB-contaminated sources is another method of PCB exposure in humans. Exposure to PCBs may also be airborne or from skin contact (Agency for Toxic Substances and Disease Registry 2001). Bioaccumulation is high with PCBs, which degrade very slowly and have the potential to mutate (Iyengar 2005). Therefore, the site in question is undoubtedly at risk for PCB contamination for two main reasons. First, the companies dumping waste on the site had been operating before the PCB ban. Second, the presence of PCBs on site means that the local groundwater, the stream, and its fish are also likely to be contaminated.

Chromium Waste

Unlike PCBs, chromium is a natural chemical element. Some forms of chromium are necessary for the human body. Trivalent chromium (chromium III) "is an essential nutrient required by the human body to promote the action of insulin in body tissues so that sugar, protein, and fat can be used by the body," (U.S. Department of Health and Human Services 2000). The chromium compounds used in manufacturing are, of course, different. Hexavalent chromium (chromium IV) is a potentially toxic industrial by-product that has been identified on this site. Chromium IV has been classified as a human carcinogen, especially implicated in lung cancers (EPA 2000). However, hexavalent chromium has not been banned in manufacturing. Although the chemical is regulated it is still being used in the manufacturing and processing of a range of materials including leather and metals.

Although chromium IV levels in food and water are "generally low," residents living near manufacturing plants that use hexavalent chromium are at risk for exposure (U.S. Department of Health and Human Services 2000). Human beings readily absoreb hexavalent chromium when it is in the atmosphere (U.S. Department of Health and Human Services 2000). Abnormally high levels (measured as greater than 2 ?g/m3) of hexavalent chromium can cause anything from a runny nose to cancer (U.S. Department of Health and Human Services 2000).

Acrylamide

According to the National Cancer Institute (2008), acrylamide is used widely in industry, such as in paper, dye, and plastic manufacturing and in the treatment of both drinking water and wastewater. The chemical can occur naturally as a result of heating food, too. When food is heated at high temperatures, acrylamide is a by-product. Cigarette smoke can also be a source of exposure to acrylamide. Acrylamide does not bioaccumulate (EPA 1994). Still, acrylamide may be a carcinogen for humans and may also cause nerve or neurological damage (U.S. Food and Drug Administration 2009; National Cancer Institute 2008).

Tolulene Diisocyanate (TDI)

Toluene diisocyanate (TDI) is an "extremely toxic" chemical used in the manufacturing of polyurethane products (EPA 2007). Exposure in both the short-term and long-term may be harmful (EPA 2007). Factory emissions are the primary source of TDI exposure. Yet because TDI does not bioaccumulate, factory workers are at the highest risk of exposure. When it is dissolved in water, TDI biodegrades into an inert material (Allport, Gilbert & Outterside 2003).

Risk Assessment

Based on the literature, PCBs and hexavalent chromium are the two most critical toxicology issues with this site. Tolulene Diisocyanate (TDI) cannot bioaccumulate and even if it did enter the stream or groundwater should not be causing a problem to local residents or fishermen. However, tests should still be done to determine whether fish metabolize TDI by-products differently than humans. Acrylamide is also not a major risk factor in this case because the chemical does not bioaccumulate and the site has not been used for manufacturing for quite some time.

Human and non-human exposure to PCBs and hexavalent chromium is the main toxicology concern. Air, surface, and water sources may be at risk of contamination. Risk assessment should include testing the ground water, including the source of the stream and also the access point for local water. Local soil should be tested for toxins, and air samples should also be taken. The fish must be tested as well, given that the stream is popular among local anglers.

The four steps of risk assessment include Hazard Identification, Dose (response assessment), Exposure Assessment, and Risk Characterization. We have identified the hazards as PCBs and hexavalent chromium, both of which are classified as potential carcinogens and which may also cause acute and/or chronic health problems in humans. An exposure assessment has revealed that ingestion is likely to be the main exposure point of entry for PCBs, whereas inhalation is likely to be the main point of entry for exposure to hexavalent chromium. The risks are characterized as high, and therefore all the following recommendations should be implemented immediately.