Located about one mile upstream from a residential area, conditions at the site in question are similar to those involved in many abandoned industrial sites across the country where there has been little attention paid to remediating the leftovers from chemical-intensive commercial operations. The site had been in continuous use for the past 6 decades by two different companies and approximately one hundred unmarked 55-gallon drums are buried around the site which carry a strong chemical odor. This is not surprising since the drums in particular are in poor shape and many are rusted out and cracking in places Although the drums are unmarked, it is known that wastes from the previous industrial activities included: (a) PCBs; (b) chromium waste; (c) acrylamide; and (d) toluene diisocyanate (TDI). In addition, a stream that is favored for fishing meanders through the site and local residents also use a location about one mile downstream from the site as a local potable and irrigation water source.
An analysis of each of the known wastes at the site.
Description of the issue and the purpose for the report. The issues involved in this toxicology report concern identifying the specific toxicants that are involved and their potential effects on humans (Toxicology report law, 2012, para. 1). Therefore, the purpose of this report is identical for each of the toxicants involved which will include an overview of the known wastes from the site in question, a description of their common routes of exposure, mechanisms of toxicity, and their respective exposure limits. A brief overall risk assessment of the site based on these four risk assessment steps is followed by recommendations concerning what actions should be taken at the site based on the toxicological assessment.
Polychlorinated biphenyls. Commonly referred to by their acronym, PCB, polychlorinated biphenyls are organochlorine contaminants that are among the more stable and pervasive toxicants encountered by humans today (Liberda, Tsuji & Wainman, 2007).
Chromium waste. This toxicant is a common material used in the automotive industry (Smith, 1998) as well as in nuclear reactors and treatment systems (Rayl, 2003). To date, some commercial applications have been developed that use chromium waste as a raw material (Smith, 1998). In other cases, though, chromium waste accumulates in the air, soil and water in and around abandoned industrial sites and the substance is known to be highly carcinogenic (Sharma, 2005).
Acrylamide. This crystalline solid is white, odorless, and is flake-like in appearance; the current primary application for acrylamide is for drinking water treatment, but it is also used in to improve production from oil wells; make organic dyes and chemicals, sizing of paper and textiles; ore processing; and the construction of dam foundations and tunnels (Acrylamide consumer fact sheet, 2012). A suspected carcinogenic, acrylamide is commonly found in the sealants used in dams (where its toxic effects were first studied) as well as the textile and paper industries and the substance can contaminate groundwater sources and is known to cause peripheral neuropathy (Timbrell, 2005).
Toluene diisocyanate (TDI). The compound dinitrotoluene (DNT) is typically used to manufacture toluene diisocyanate (TDI) which is used to make polyurethane foams, elastomers, and protective coatings (Butrica & Douglas, 1990)
Description of the toxicants' common routes of exposure
PCBs. Generally, PCBs enter the environment through routes of exposure such as leakage from transformers containing the toxicant, as well as accidental spills and industrial discharges (Liberda et al., 2007)
Chromium waste. Chromium waste dust is frequently carried by the wind into nearby residences where it can be directly inhaled or accumulate on residence interiors where it can eventually become resuspended in the air (Lioy, 2010). For instance, a chromium waste remediation project in New Jersey sampled dust in numerous residences located on or next to chromium waste-contaminated land (Lioy, 2010). In this study, Lioy reports that, "Exposure pathways and levels of chromium showed that people living in homes adjacent to or on a site had higher indoor levels and urine levels of total chromium. The high levels were attributable to resuspended particles, dust blown off the surface of the waste sites with high chromium, or chromium tracked indoors by residents, friends, and pets" (2010, p. 1082).
Acrylamide. Groundwater can be contaminated with this substance, thereby exposing entire populations to risk; beyond the potential carcinogenic effects of acrylamide, there has also been evidence of nervous system damage identified in the research to date (Timbrell, 2005).
Toluene diisocyanate (TDI). The EPA's Action Plan (2011) for TDI states that, "Diisocyanates are well-known dermal and inhalation sensitizers in the workplace and have been documented to cause asthma, lung damage, and in severe cases, fatal reactions" (p. 1).
Mechanisms of toxicity
PCBs. The mechanisms of toxicity for PCBs include its ability to bioaccumulate over time, meaning that the entire food chain in this area can be adversely affected. Moreover, PCBs are known to strongly resist degradation, meaning they can linger in the environment for a number of years and eventually wend their way into the upper levels of the food chain, including humans; in fact, the upper levels of the food chain will experience higher levels of contamination because of the toxicant's tendency to bioaccumulate (Liberda et al., 2007).
Chromium waste. The U.S. Environmental Protection Agency (EPA) fact sheet for chromium states that it occurs in the environment primarily in two valence states: (a) trivalent chromium (Cr III) and (b) hexavalent chromium (Cr VI); human exposure to these ions can take place from either industrial or natural sources of chromium, with chromium III being far less toxic compared to chromium (VI) (Hazard summary, 2000). According to the EPA's factsheet, "The respiratory tract is also the major target organ for chromium (III) toxicity, similar to chromium (VI). Chromium (III) is an essential element in humans. The body can detoxify some amount of chromium (VI) to chromium (III)" (para. 3). Likewise, for chromium (VI) toxicity, the respiratory tract is also the major organ targeted for both acute (short-term) and chronic (long-term) exposures resulting from inhalation (Hazard summary, 2000). A number of respiratory problems have been linked with exposure to chromium (VI); in addition, the EPA cautions that inhaled chromium (IV) is a known human carcinogen that contributes to a higher prevalence of lung cancer (Hazard summary, 2000).
These findings are congruent with the results of a study by Layan and Paine (2001) who emphasize that although more research is needed in this area, there is a growing consensus in the scientific community that one chromium ion in particular, Chromium (VI), is responsible for the majority of the compound's toxicity. For example, according to Dayan and Paine (2001), "There is good evidence from the clinic and the laboratory that Chromium (VI) is the ion responsible for most of the toxic actions, although much of the underlying molecular damage may be due to its intracellular reduction to the even more highly reactive and short-lived chemical species Chromium (III) and Chromium (V)" (p. 439). The research to date also indicates that Chromium (VI) exposure can cause point mutations in DNA as well as damage to chromosomes; in addition, exposure to Chromium (VI) has also been shown to cause to affect formation and can result in oxidative changes in proteins (Dayan & Paine, 2001). The precise role of these various chromium ions on the incidence of tumors and allergy sensitivity in humans remains unknown (Dayan & Paine, 2001).
Acrylamide. As noted above, groundwater represents the primary mechanism by which acrylamide is consumed by humans, but steps to improve the commercial applications of acrylamide in recent years have controlled contamination within acceptable levels (Consumer factsheet on acrylamide, 2012). When exposed, though, the EPA determined that when exposed to excessive levels, acrylamide has the potential to cause several short-term effects, including (a) damage to the nervous system, (b) weakness and (c) incoordination in the legs; in addition, inordinately high lifetime exposures to acrylamide can cause damage to the nervous system, paralysis and cancer (Consumer factsheet on acrylamide, 2012).
Toluene diisocyanate (TDI). According to the EPA's Action Plan for TDI, exposures to diisocyanates can take place across a wide array of settings ranging from "production facilities from small workshops to automated production lines" and both inhalation and dermal contact can cause respiratory ailments including asthma, dermatitis and immune sensitization (p. 2).
Exposure limits for the toxicants
PCBs. Although there have been efforts at the national and international scale to develop acceptable daily exposure limits for PCBs for food products such as salmon in Canada, there has not been any substantive progress in this area and Canada is currently the only country that has established exposure limits for PCBs (Liberda et al., 2007).
Chromium waste. The Occupational Safety and Health Administration's permissible exposure limits for chromium are expressed as a time-weighted average defined as "the concentration of a substance to which most workers can be exposed without adverse effect averaged over a normal 8-hour workday or a 40-hour workweek" and there are different exposure limits for each of…