Concerns About Specific Substances

The UK s Enviromnent Agency has defined three classes of chemicals that require special environmental management. They include plastics additives generally, and brominated flame retardants and chlorinated paraffins in particular. Perfluorinated chemicals are specifically identified. 

Many of the chemicals currently attracting controversy are plastics additives, and several have been suspected of being endocrine disrupters. The Friends of the Earth has a league table of retailers, in which the winners are the ones that are most advanced towards phasing out the sale of products containing suspected endocrine disrupters such as phthalates. At the moment, bisphenol A is not classified as an endoerine disrupter in the USA, but the Japan Environmental Agency has added DEHP to its short list of alleged endocrine disrupters, which also includes dibutyl phthalate and dicyclohexyl phthalate. 

Nonyl phenol has been assigned a Category 3 risk by EU scientists, whereas bisphenol A is classified as more serious at Category 2, specifically referring to fertility. The EU will ban nonyl phenol in certain applications from January 2005. It is expected that efforts will be made to avoid the octyl ones being adopted as replacements. 

In fact the European Union has now cleared DEHP fiom any association with harm to public health, on the grounds that exposure levels are at least 700 times lower than the current safe levels. Discussions continue in relation to the other two major phthalate plasticisers, DINP and DIDP. Benzyl butyl phthalate rates Category 2 for adverse fertihty effects, but only Category 3 for its effects on human development. 

There are four areas of EU concern (a) children s toys, (b) certain medical devices, (c) workplace exposure and (d) public exposure close to factories. This is a much narrower area of concern than that expressed by Greenpeace, which has campaigned against the use of phthalates and PVC in many apphcations. 

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A person can meet criteria for abuse or dependence for one drug and not others, although there is concern about what has been referred to as cross-addiction. Cross-addiction means that a person who is dependent upon one substance may be dependent upon another, very similar one. An example might be a person who is diagnosed as dependent upon tranquilizers and who, you may fear, is also addicted to a similar substance such as alcohol. However, the research is not entirely clear on whether cross-addiction occurs, and I have known clients who had very specific problems with one substance who did not generalize into problems with other, similar substances. A person also may meet criteria for abuse or dependence for multiple substances generally, this is referred to more simply as substance abuse or substance dependence. 

The Danish Environmental Protection Agency has started work to draft a national plan to control brominated flame retardants, and has published what officials claim to be the most exhaustive national survey analysing the flow of such substances and assessing possible substitutes for specific applications. The survey found that the major source of BFRs emissions in Denmark was from evaporation from products already in use, and underlines previous concerns about the possible harm due to bioaccumulation. Denmark is to join Sweden in urging international action to curb the use of brominated flame retardants. 

Limits on the migration of specific substances of toxicological concern span the concentration range from 0.01 mg/kg to about 60 mg/kg. The lower limits are... 

The general concern about limiting off-site releases of hazardous substances is the primary reason why classification of waste based on risks to hypothetical inadvertent intruders at waste disposal sites does not provide a substitute for site-specific risk assessments when determining acceptable disposal practices. Nonetheless, experience with risk assessments at near-surface disposal sites for low-level radioactive waste has indicated that, for most radionuclides, disposal limits that provide adequate protection of future inadvertent intruders should provide adequate protection of the public and the environment at off-site locations as well. Exceptions are expected to occur only in unusual cases of long-lived and highly mobile radionuclides. 

The mole is associated with a specific chemical entity as defined by its chemical formula [15], Its structural formula, isotopic composition, isomeric form, crystal structure, or chirality may have to be given in order to completely specify the entity of interest. The achievable uncertainty of amount-of-substance measurement is limited by that of its apparent molar mass. This consideration affects not only measurements on entities with variable molar mass, but those on pure substances. It is related to the traditional and important concern about purity. 

Many countries have also established specific regulations to protect children from exposure to certain environmental hazards, including toxic chemicals. Examples include banning of heavy metals in toys, strict limit setting for persistent toxic substances in baby foods, and the setting of environmental limit values derived on the basis of infants sensitivities (e.g. nitrates in drinking-water). In the United States, concerns about children s special vulnerabilities... 

Looking around the corner, there are a number of sustainability issues that could be financially material in the chemical sector. The research on body burden, or what trace (and otherwise) substances exist in humans as a result of environmental exposure is perhaps the most troubling in that little is known about how this occurs, especially among populations that are not in proximity to known sources. Look for the level of concern on this issue to rise and for potential societal and policy push-back fuelled by the uncertainty. Body burden could serve as a gateway issue to a wide range of actions by civil society on a whole host of specific substances and pathways of exposure. In particular, results that pertain to body burden in children have a huge emotional resonance beyond the scope of most issues of pollution. ... 

MRL users should be familiar with the toxicologic information on which the number is based. In particular, the user should review the profile of the specific substance of concern (see Appendix A). Section 6.7, "Relevance to Public Health," contains basic information known about the substance. Other sections such as 6.9, "Interactions with Other Substances, and 6.10, "Populations that are Unusually Susceptible" provide important supplemental information. 

One of the two nanoparticles that was the subject of the November 2008 SNUR is a siloxane modified silica nanoparticle, and the other is a siloxane modified alumina nanoparticle. EPA explained in the SNUR that it was concerned about dermal and inhalation exposures for new uses that were not described in the PMNs filed for those substances. It suggested that a ninety-day inhalation toxicity test would help characterize the human health effects for each substance. The SNURs for these two substances say that it would be a significant new use to use either substance without specified personal protective equipment, for any use other than the uses specified in the PMNs for those substances, and to manufacture, process or use them in powder form. The preamble to the SNUR says that the PMNs do not claim confidentiality for use of these substances as additives, but the PMN for one of these substance clearly limits the kind of additive for which it was intended, but everything except the word additive is claimed as confidential. Therefore, any other entity that intends to manufacture, import, or process any nanoparticles described by the generic names for these substances should submit a bona fide letter to determine their exact chemical compositions and the specifics of what uses are significant new uses. 

Ultimately the analyst can never rule out a false positive, or the interference of some highly similar species that has not been considered. Professional judgment, the time and budget available will indicate to what extent experiments must be done to demonstrate specificity. As long as these are done and documented to the client s satisfaction, the method is considered properly validated. If a future user of the method has particular concerns about other interferences, then revalidation should be undertaken to study these substances. 

We noted from the outset of this chapter that environmental concerns about ozone depletion arise from tbe increase in the rate of destruction of ozone in the stratosphere. This is a process apparently caused by man-made chemicals. Specifically, chlorofluorocarbons used as refrigerants have been cited as a cause of ozone depletion. Yet a look at the Chapman cycle does not show any obvious role for CFCs. So how can these molecules accelerate the destruction of ozone if they do not even appear in the underlying chemical equations Catalysis is a process in which a reaction rate is influenced by the presence of substances that are neither reactants nor products in the overall equation. A catalyst is a substance that increases the rate of the reaction but is neither created nor destroyed in the process. How can CFCs catalyze ozone depletion ... 

In the previous sections, we indicated how, under certain conditions, pressure may be used to induce immiscibility in liquid and gaseous binary mixtures which at normal pressures are completely miscible. We now want to consider how the introduction of a third component can bring about immiscibility in a binary liquid that is completely miscible in the absence of the third component. Specifically, we are concerned with the case where the added component is a gas in this case, elevated pressures are required in order to dissolve an appreciable amount of the added component in the binary liquid solvent. For the situation to be discussed, it should be clear that phase instability is not a consequence of the effect of pressure on the chemical potentials, as was the case in the previous sections, but results instead from the presence of an additional component which affects the chemical potentials of the components to be separated. High pressure enters into our discussion only indirectly, because we want to use a highly volatile substance for the additional component. 

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