Risk to the environment

Toxicity. Antimony has been found not to be a carcinogen or to present any undue risk to the environment (9). However, because antimony compounds also contain minor amounts of arsenic which is a poison and a carcinogen, warning labels are placed on all packages of antimony trioxide. 

Linear alkylbenzenesulfonate showed no deleterious effect on agricultural crops exposed to this material (54,55). Kinetics of biodegradation have been studied in both wastewater treatment systems and natural degradation systems (48,57,58). Studies have concluded that linear alkylbenzenesulfonate does not pose a risk to the environment (50). Linear alkylbenzenesulfonate has a half-life of approximately one day in sewage sludge and natural water sources and a half-life of one to three weeks in soils. Aquatic environmental safety assessment has also shown that the material does not pose a hazard to the aquatic environment (56). 

The product has to present minimum risk to the environment during use and disposal. 

However, some waste will be inevitable. While some waste represents minimal risk to the environment when emitted (such as the release to the marine environment of depleted brine in chlor-alkafi production), a fully sustainable process will (other things being equal) require aU harmful emissions to be treated to ensure zero impact on the environment. This... 

The membrane cell produces a very pure caustic soda solution and consumes less energy unlike the mercury and diaphragm processes.24 Also, it poses less pollution risk to the environment unlike... 

In evaluating options for obtaining the energy needed to sustain world economic progress in the coming years, it is important to consider the full spectrum of risks to the environment and to human health that each option may create or reduce. This is particularly important in evaluating nuclear power, where often attention has been disproportionately focussed on the presumed dangers. 

Finally, in the risk characterization step, the PEC/PNEC quotient that defines the risk of the substance in the environment is calculated. If the quotient (PEC/PNEC) is less than 1, the substance do not present risk to the environment. More information is available in the European Commission Technical Guidance Document on Risk Assessment [3] and in the United States Environmental Protection Agency s Guidelines for Ecological Risk Assessment [6]. 

Besides the organic pollutants mentioned above, e-waste recycling activities are also releasing various heavy metals such as Hg, Cd, Cr, Cu, Ni, Pb, and Zn [14]. These e-waste-derived heavy metals pose extremely high risk to the environment and humans [67], especially at e-waste processing sites. Numerous previous studies suggested that most environmental matrices around e-waste sites, such as air, soil, sediment, and dust, have been severely contaminated by these heavy metals (Table 2) [71-75],... 

Disease-resistant varieties are attractive because they should pose little or no risk to the environment and enable growers to reduce and in some cases eliminate the need for pesticides. In some host-pathogen systems, resistance may persist for many years, but in others it may be short-lived (Koike et al., 2000). Unfortunately, resistance is not available to counter every disease and for some of the most damaging ones, such as tomato late blight (P. infestans) and white rot (Sclerotium cepivorum) of alliums, no acceptable resistant varieties are currently available. 

Environmental risk assessment of substances is nowadays based on an evaluation of exposure pathways and concentrations on the one hand and identification and selection of sensitive endpoints on the other. The concept is operationalised by comparing real or estimated (predicted) exposure concentrations (PEC) with calculated no-effect concentrations (NEC or PNEC, predicted NEC). The comparison can be made by calculating the quotient of exposure and no-effect concentration. If the quotient is less than one, then the substance poses no significant risk to the environment. If the quotient is greater than one, the substance may pose a risk, and further action is required, e.g. a more thorough analysis of probability and magnitude of effects will be carried out. 

The chemical characterization of atmospheric pollutants is of great importance for determining their primary sources, elucidating chemical reactions in the atmosphere, determining potential risk to the environment and developing a reasonable control strategy. 

The lack of human pathogenicity of plant viruses rules out the risks of human infection by exposure in the field or in food products to a plant virus. However, biological containment of the virus expression vector remains a primary safety concern as it can be considered a risk to the environment. This includes the spread of recombinant viruses to weeds... 

Because of the first of these uncertainties (the extrapolation across species), assessments of risks to human health apply an uncertainty or safety factor of 100 to the experimentally derived no observed adverse effect concentration (NOAEC), in other words the NOAEC is divided by 100 to derive a no-effect level for human toxicity. This factor has been used since 1961, when it was chosen on an essentially arbitrary basis (RCEP, 2003, p22). In the assessment of risks to the environment, application factors of 10, 50, 100 or 1000 are applied to the results of tests carried out on specific species,2 depending on the species used and whether the tests were long term or short term. Evidence to the Royal Commission on Environmental Pollution (RCEP) for their report Chemicals in products indicated that these are merely extrapolation factors — they express the statistical variability of test results but do not effectively take into account inter-species variability, the vulnerability of threatened species, lifetime exposures or the complexity of biological systems... 

As discussed above, the risk of chemicals in the environment is dependent on both exposure and toxicity. Pathways through which organisms in the environment are exposed to chemicals are therefore key determinants of how safe (and therefore, how green ) a chemical is, and must be considered in moving towards a reduced risk or hazard approach to the production and use of chemicals. Fate in the environment is the principal determinant of exposure and designing chemicals for reduced hazard and risk to the environment involves consideration of processes that affect the chemical in the environment, in addition to toxicity. Assessment of environmental fate, including design of chemicals for nonpersistence, is discussed in detail in Chapter 16. 

The above sections have provided background information to highlight the principles that can be applied to designing chemicals that are greener. In the following sections, we give examples of how these techniques have been applied to the design of chemicals with less risk to the environment. 

This approach to green chemistry can be very fruitful in terms of being able to tailor the properties of chemicals to minimize risk to the environment while maximizing the benefit. However, this may not always be successful because the properties that contribute to the beneficial use of the product may be the same properties that affect risk to the environment. 

Ranking and Prioritizing Pesticides in Terms of Risk to the Environment... 

By screening chemicals for properties that increase risk to the environment, it is possible to move towards the production of safer commercial products. The design of chemicals with reduced potential for adverse effects in the environment may be complicated by a tradeoff between the properties of the chemical that confer benefits and those that confer risks to the environment. This is not new and is an issue with all human activities. In fact, the adverse effects of chemicals synthesized for use by humans may be far less significant in the environment than other activities such as urbanization, use of fossil fuels, and conversion of natural areas to the production of food and fiber. Clearly, the quest for greener chemicals must be conducted in a framework of the evaluation of risks and benefits to humans and the environment. 

There is no formal framework for identifying green chemicals and using this framework in intelligent design for lower risk to the environment. There are, however, a few properties that are key to this objective. Fate in the environment... 

Figure 15.9 Graphical illustration of a decision tree for the design of chemicals with lower risk to the environment.

This provision is unlikely to be used in practice but it could be used to restrict sales of a pharmaceutical which, post launch, was found to be posing an unacceptable risk to the environment... 

---