Chemicals that Should Not be Profiled

There are a number of chemical classes that should not be investigated using the current version of the PBT Profiler. Important classes of chemicals that should not be profiled are provided below. This is not an exhaustive list. Expert assistance is available from the developers of the PBT Profiler.

Inorganic Chemicals

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The estimation methods used for the PBT Profiler were designed and developed for organic chemicals. Inorganic chemicals will not provide reliable results and should not be profiled. This category of chemicals is defined as all chemicals that do not contain Carbon. It includes neutral species such as titanium dioxide (TiO2) and inorganic salts, such as sodium chloride (NaCl) or potassium permanganate (KMnO4). This class of chemicals also includes organo-metallic chemicals (chemicals that contain carbon bonded to a metal species). If a chemical contains any of the elements in the following table, it should not be profiled: He Li Be B Ne Mg Al Ar Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Kr Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te Xe Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn Fr Ra Ac Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr

Sodium, potassium, and ammonium salts of organic acids, such as sodium acetate, can be run through the PBT Profiler. This is discussed in the salts section, below.

Reactive Chemicals

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Chemicals that are known, or suspected, to be reactive should not be profiled. This category is for those chemicals that would be expected to have a half-life of less than 60 days under "normal" environmental conditions because they would meet the criteria of the "not persistent" category. Highly reactive chemicals, therefore, would not be expected to persist in the environment for long periods of time (and as a result, they would not be expected to bioaccumulate). It is important to note, however, the highly reactive compounds may display acute (short term) toxicity, and this should be considered in a P2 assessment on them. Examples of reactive chemicals are provided in the following table. This list is provided to demonstrate the types of chemical processes that may lead to rapid degradation. An important sub-class of reactive chemicals are those that undergo rapid hydrolysis (react with water). Thermally reactive chemicals such as peroxides (non-stabilized) would be expected to decompose at or near room temperature. Chemicals that contain iodine (such as butyl iodide), conjugated double bonds (such as quinone and TNT), and other reactive groups (such as substituted disulfides) may rapidly decompose upon exposure to UV light. In the environment, UV radiation in sunlight may cause these chemicals to undergo direct photolytic degradation. Environmental photolysis is expected to occur primarily for chemicals that partition to the atmosphere; however it may also occur in the upper layers of water (such as lakes, rivers, and streams), or on plant and soil surfaces. When performing a P2 assessment for chemicals that may undergo photolyis, it is important to note that the half-life will be dependent on the amount of available sunlight. Factors that determine the amount of available sunlight include geographic location (e.g., latitude), time of day, time of year, and weather conditions. Examples of chemicals that undergo hydrolysis Chemicals that react rapidly with water and are converted to other substances (hydrolysis products) should not be profiled. The estimation methods used by the PBT Profiler were designed for the parent compound, not its hydrolysis product. The likely result from profiling chemicals that rapidly hydrolyze is that their persistence will not be accurately estimated (the persistence of these compounds is likely to be overestimated). Organic chemical classes that are known to rapidly hydrolyze include: Acid Halides Isocyanates Sulfonyl Chlorides Siloxanes alpha-Chloro ethers If you have a chemical that rapidly hydrolyzes, then the hydrolysis products can be run through the PBT Profiler. This will provide an indication of the potential effects associated with the release of your chemical to the environment.

If you suspect that your chemical may fall into the highly reactive class, a P2 assessment can still be performed by identifying the degradation products and running them through the PBT Profiler. For example, peroxides would be expected to degrade to a pair of corresponding alcohols (or only a single alcohol for a symmetrical peroxide). These alcohols could then be profiled to determine their potential for persistence, bioaccumulation, and toxicity. Many other chemical classes are known to be reactive or rapidly hydrolyze and would be expected to have a half-life of less than 60 days. If you suspect that your chemical is reactive, the results of the PBT Profiler should be used with caution and only after review by a trained expert in environmental fate processes and/or aquatic toxicity. Assistance is available from the developers of the PBT Profiler.

Salts (Organic Salts)

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The PBT Profiler will provide results for organic salts; however, the results for these chemicals cannot be validated because of the limited experimental data available on these compounds. The physical/chemical properties and environmental fate of a small number of organic salts are well documented in the environmental literature. Therefore, only the following organic salts should be profiled: Sodium (Na) salts Potassium (K) salts Ammonium (NH4+) salts Salts of the other group I, group II, transition metal, actinide, and lanthanide cations should not be profiled. More information on elements that should not be profiled is provided in the discussion on inorganic chemicals, above. If your chemical contains one of these cations, contact the developers of the PBT Profiler for assistance.

High Molecular Weight Compounds

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Polymers and chemicals with a molecular weight greater than 1,000 should not be profiled as the physical property estimation methods were not developed for these types of compounds. However, many polymers may be made up of dimers, trimers, and oligomers that have a molecular weight of less than 1,000. These smaller molecules may contain the same components of the larger polymers, and, therefore, could be run through the PBT Profiler when performing a P2 assessment. The results should be interpreted with due caution, however, as the persistent, bioaccumulation and toxicity characteristics of chemicals with a molecular weight of >1,000 are likely to be significantly different than much smaller compounds, even if they have similar structures. Contact the developers of the PBT Profiler for assistance with assessing polymers and other high molecular weight species.

Chemicals with Unknown or Variable Composition

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The PBT Profiler was developed for discrete organic chemicals. That is, organic chemicals that can be represented by a single, precisely known chemical structure. If the compound has a variable composition, (such as oligomers, natural fats, or a product mixture that changes composition depending on the reaction conditions), then the results provided by the PBT Profiler may not accurately reflect the true nature of the commercial product. The PBT Profiler uses a discrete chemical structure as its input. If a chemical with unknown or variable composition is profiled, then a representative structure has been entered. It is possible that the representative structure may not represent the commercial product and, therefore, the PBT Profiler results may not be accurate. If you have a chemical of unknown or variable composition that you think can be run through the PBT Profiler, you can contact the developers of the PBT Profiler for assistance.

Mixtures

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Mixtures cannot be run through the PBT Profiler because it uses a single, discrete chemical structure as its input. If the chemical you want to profile is a mixture of discrete organic substances, then each substance can be run through the PBT Profiler separately and the result can be compared and contrasted. If there is one component of a mixture that predominates, then it may be used to represent the entire mixture (i.e., a representative structure can be entered). If this procedure is performed, the results should be interpreted with caution, as other components of the mixture may possess significantly different persistence, bioaccumulative, and toxicity properties. If you need to run a mixture through the PBT Profiler, and require assistance, contact the developers of the PBT Profiler.

Surfactants

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Surfactants should not be run through the PBT Profiler. Surfactants do not typically dissolve in water; instead, they tend to form micelles (dispersed aggregates of the surfactant molecules). Because they form dispersion, their water solubility and other environmental fate parameters cannot be accurately estimated using the methodology employed by the PBT Profiler. Many different types of chemicals have surfactant properties and there is no sharp distinction between those that do and those that don't. Surfactants fall into three categories: detergents, wetting agents, and emulsifiers. The following table provides examples that should not be run through the PBT Profiler and includes the classical ionic surfactants and typical non-ionic surfactants. In general, a compound with a polar functional group (e.g., carboxylate or sulfonate) with a long (> 10 carbons) non-polar chain can be considered a surfactant. A similar compound with a relatively short chain can be profiled although the results should be considered with caution. For non-ionic compounds, those with a relatively large number of repeating units should not be profiled. Since no sharp cutoff for chemicals in this class exists, contact the developers of the PBT Profiler for assistance on surfactants. The classic "soap" molecule is a fatty acid salt The most widely used group of modern detergents are linear alkyl sulfonates (LAS) Alkyl benzene sulfonate detergents, which are not widely used due to their persistence in aquatic environments. Polyethylene and polypropylene oxide substituents represent the largest class of non-ionic surfactants. Many fluorinated chemicals are used as surfactants or have surfactant properties.

Highly Fluorinated Compounds

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Many highly fluorinated chemicals (those that have more fluorines than non-fluorine atoms bonded to carbon), including fully fluorinated organics (those that have all hydrogens on carbon replaced with fluorine), possess physical/chemical and environmental fate properties that are vastly different than their non-substituted analogs. The models used by the PBT Profiler do not accurately predict the unique characteristics of these materials, although the estimation methods are continually improving as more data become available. Given the characteristics of these compounds, all per- and highly- fluorinated chemicals should not be profiled. It should also be noted that many highly fluorinated chemicals may be used as surfactants and should not be profiled for the reasons discussed in the surfactant class. A fully fluorinated compound where all the hydrogens bonded to carbon have been replaced with a fluorine An HCFC, an example of a highly fluorinated compound