In a review of 509 Confirmed Release Sites there were approximately 150 carcinogenic or potentially carcinogenic compounds mentioned in a little more than 2900 reports. These chemicals could be broken down into different classes in a variety of ways.
In terms of carcinogenicity and severe toxicity, it was found that the largest numbers of chemical reports filed were for confirmed carcinogens, followed by questions carcinogens (carcinogens still being investigation for further confirmation of this claim), followed by a mixture of chemicals that were either fetotoxic (toxic to the fetus in the womb), mutagenic but not confirmed for the carcinogenicity, or teratogenic (toxic to the embyo during its early development stages, during which time the ectoderm (skin layer and glandular system), endoderm (intestinal lining and nervous system layer), and mesoderm (pretty much everything in between) are defined. This can lead to the maldevelopment of various organ systems, which usually lead to abortion, but on occasional lead to malformed births like microcephaly, partially developed limbs, internal organs malformation, and spinal bifida.
In terms of chemical groups, throughout this study to total chemicals have been broken down in several ways.
The method applied for the first rendering of the data differentiates the most commonly known chemical groups from the various industrial toxins, which are lumped together for the moment. Examples of chemicals classified as Elements consisted mostly of the known carcinogen Arsenic. Those classified as metals included primarily Mercury and the organic Mercury compounds. The polyaromatic hydrocarbons (PAHs) and consisted primarily of monobenzenes or phenols, biphenyls, and polyphenols (i.e. 3- and 4-benzene ring coal industry derivatives). The Petroleum industry products (Petrols) were the typical oil and gasoline industry products. The often discussed non-specific Volatile Organic Compounds (VOCs) made up an exceptionally small percentage of these reports. Agricultural pesticides and herbicides defined the Agritox group.
Fitting this classification system into the first method developed, which related chemical to their carcinogenicity and genotoxicity toxicity to genetic information or genetically-related fetal/embryo development habits in a non-carcinogenic fashion), we find that the propensity of chemicals of suspected or confirmed carcinogenicity are either metals, industrial chemicals or agritoxins.
In terms of dispersal across all forms of toxicity or carcinogenicity, some groups are found in just one or two locations. The Petrol chemicals are pretty much similar in chemistry and toxicity and lack for the most part side groups that tend to make them drastically different from one chemical to the next in terms of carcinogenicity; the same can be said for PAHs. Such is not the case for agritoxins or elements (esp. Arsenic), which demonstrate significant evidence for being carcinogenic and are therefore found primarily in the confirmed carcinogens counts for these CRI sites.
The most widely dispersed chemical group in terms of toxicity are the industrial chemicals. The reason for this dispersal is obvious–the industrial chemical class is in further need of further sub-dividing of its most important toxins and carcinogens. (What do you expect for a first time?)
The second attempt to reclassify the chemical groups from CRI sites information resulted in a more applicable dataset for analyzing toxicity and carcinogenicity in relation to chemical release based on a chemicals reclassification system. This would later become very useful for mapping the chemical information spatially, and later in the development of maps depicting the theoretical spatial distribution of these chemicals in general, with individual maps developed in order to depict the distribution of a single chemical groups with specific risks tied to it, for example the highly carcinogenic halogenic aromatic compounds and possibly PAHs and Petrols, versus the non-carcinogenic, highly myoneurotoxic cyanide derivatives.
In the following breakdown, the highly carcinogenic organic Mercury is distinguished from its less fatal metallic form, and the industrial chemicals previously defined mostly based on SIC [standard industrial classification] information (for example industries with a non-PAH note and/or non-petrol-related SIC) are now differentiated in aromatic compound producers, and aromatic and non-aromatic halogenic (mostly Fluorine or Chlorine) compound producers. This latter feature has implied in it the difference between the most common non-aromatic producers–the dry cleaning facilities–from the industrial sites that frequently release aromatic halogenic compounds like chlorobenzenes.
Bringing the analysis just one step further, in term specific intergroup-subgroup relationships, for example PAHs versus their independent risk for being confirmed carcinogenic versus a mixture of questionable and confirmed carcinogens, the following two dimensional provide us with more insight as to specific risks attached to specific chemical groups.
Counts (it is difficult to see, but in this rendering 'Industrial Chemicals' is the most common (highest peak) followed by petrols and heavy metals)
When this is viewed in terms of percentages, we find that a number of chemical groups, although they consist of a few reports and a few number of CRI sites, rank highly in terms of their carcinogenicity. They may be scarely found in a CRI, but when they are present at a site, they have the potential of becoming the primary reason for initiating a clean-up.
Percentages (note high peaks in several other groups including agritox, petrol, PAH, and VOCs)
[NOTE: Examples of how this was applied to the second method of site chemical reclassification is demonstrated on other pages in this review of the project.]
Brian Altonen, MPH, MS 