Chemicals risk assessment types

Trial and error is often the typical procedure that is used to implement enhanced biorestoration. In simple cases of gasoline cleanups, these may be appropriate however, when the chemicals involved are recalcitrant (difficult to degrade), toxic, or present in a complex geologic environment (i.e., low-permeability soil, lateral or vertical heterogeneities, etc.), enhanced biorestoration can be difficult, and risk assessment-type analyses may be more suited for a particular site. 

The European system for regulating synthetic chemicals, described in Chapter 5, is predominantly risk-based . This means that restrictions on the manufacture or use of chemicals must be justified by reference to evidence that there is a risk of the chemical causing a specified type of harm. REACH (Registration, Evaluation, Authorization and restriction of Chemicals) does not define the term risk , but the directive on risk assessment of new substances defined it as the incidence and severity of the adverse effects likely to occur [...] due to actual or predicted exposure to a substance (Article 2 of Directive 93/67/EEC). In the first part of this chapter I look at how risks from chemicals are assessed. What does chemicals risk assessment in practice aim to achieve Can it provide the reliable evidence needed for agreement by all parties on whether or not a chemical poses a risk My answer to this second question is no there are multiple uncertainties in chemicals risk assessment which lead to protracted debates as to whether a chemical poses a risk or not. 

A risk assessment for explosivity, oxidising properties and flammability is required unless none of the product s constituents possess such properties, and, in addition, that on the basis of information available the product is unlikely to present dangers of this kind. Due to the type and nature of the studies conducted under the physicochemical data requirements section (see Tables 1 and 2 for a list of the required studies on the active substance and 23 product types to fulfill the BPD), a physico-chemical risk assessment on a particular product is usually qualitative and is based solely on the intrinsic hazards of the constituents. Therefore, the outcome of a physicochemical risk assessment usually relies on the eventual classification of the product for physical and chemical characteristics and this then leads directly to risk management proposals. 

A risk assessment is performed in four steps hazard identification, analysis of exposure, analysis of effect, and risk characterization. The same general process is used to assess risk from many different types of threats, not just toxic chanicals. Risk assessments are performed for individual chemicals. When exposure is to a mixture of chemicals, risk assessments are performed for each individual chemical in the mixture. Generally, the health risks from individual chemicals are added together to estimate the total health risk from the mixture of chemicals. In other words, health risks are generally considered to be additive. If there is evidence that two chemicals either enhance or interfere with each other s toxicity, then that information is factored into the risk assessment, usually in the risk characterization step. 

Hazard identification involves gathering and evaluating data on the types of health injury or disease that may be produced by a chemical and on the conditions of exposure under which injury or disease is produced. It may also involve characterization of the behavior of a chemical within the body and the interactions it undergoes with organs, cells, or even parts of cells. Hazard identification is not risk assessment. It is a scientific determination of whether observed toxic effects in one setting will occur in other settings. 

Since 1970 tlie field of healtli risk assessment Itas received widespread attention witliin both tlie scientific and regulatoiy committees. It has also attracted tlie attention of the public. Properly conducted risk assessments have received fairly broad acceptance, in part because they put into perspective the terms to. ic, Itazard, and risk. Toxicity is an inlierent property of all substances. It states tliat all chemical and physical agents can produce adverse healtli effects at some dose or under specific exposure conditions. In contrast, exposure to a chemical tliat lias tlie capacity to produce a particular type of adverse effect, represents a health hazard. Risk, however, is tlie probability or likelihood tliat an adverse outcome will occur in a person or a group tliat is exposed to a particular concentration or dose of the hazardous agent. Tlierefore, risk can be generally a function of exposure and dose. Consequently, healtli risk assessment is defined as tlie process or procedure used to estimate tlie likelihood that... 

There is a continuing interest in the development of biomarker assays for use in environmental risk assessment. As discussed elsewhere (Section 16.6), there are both scientific and ethical reasons for seeking to introduce in vitro assays into protocols for the regulatory testing of chemicals. Animal welfare organizations would like to see the replacement of toxicity tests by more animal-friendly alternatives for all types of risk assessment—whether for environmental risks or for human health. 

Besides the LCA approach, also risk assessment can be performed analysing the chemical compounds or modelling via predictive exposure models. Both types of approaches have their justification to measure environmental concentrations of chemicals in the environment with laboratory measurement is still the most reliable way for determination. But it goes along with the disadvantage of high investments concerning time and money. Besides that laboratory approaches are limited in terms of space and time, and in consequence, the survey of many micro-pollutants and their... 

These are the most important types of problem that arise which must be dealt with if risk assessments are to be completed. Again, there may be data available for some chemicals that allow reasonably accurate scientific answers for some of these questions, but as we emphasized in Chapter 7, scientific answers will generally be found wanting. Hence invocation of science policies - defaults. In Table 8.2, we find the most important regulatory defaults for risk assessment. 

There are several large impediments to achieving the goal of more accurate risk assessments. First, it often requires a considerable investment in the research necessary to uncover the types of information needed to replace default assumptions in specific cases. If one hypothesizes that di-(2-ethylhexyl)phthalate (DEHP, a real and important chemical) produces liver tumors in rodents by mechanisms that either do not apply to humans at all, or that do not operate at low (human) doses, or both, then there arises the question of what type of research information is necessary to test the validity of such hypotheses If such research is actually carried out, then what type of results from that research would allow conclusions to be drawn about the validity of the hypotheses In many specific cases creative and knowledgeable scientists can hypothesize alternatives to the usual defaults and ways to test their validity. But it often turns out to be difficult to arrive at... 

The risk assessment framework we have described for chemical toxicity is applicable to microbial risk assessment. Once the information is available on microbial hazards, which are for the most part acute (immediately observable) conditions resulting from acute (one-time) exposures, and their dose (pathogen count)-response characteristics, we should be ready to assess the risks associated with any dose of interest. Hazard information for the important pathogens is readily available but, as expected, their dose-response characteristics are much harder to come by. So with pathogen risk assessment we see the same types of uncertainties creeping into the framework as we have encountered for chemicals. 

Many other OECD activities on hazard/risk assessment are undertaken within programs such as Existing Chemicals, New Chemicals, and Pesticides and Biocides, which deal with specific types of chemicals. The work on exposure assessment methods is undertaken by the Task Force on Environmental Exposure Assessment, consisting of experts. Most of the outcome of this work is published in the Series on Testing and Assessment or in Emission Scenario Documents, which are available at the OECD Web site (OECD 2006a). 

Gronlund (1992) has investigated methods used for quantitative risk assessment of non-genotoxic substances, with special regard to the selection of assessment factors. Gronlund found that humans, in most cases, seem to be more sensitive to the toxic effects of chemicals than experimental animals, and that the traditional 10-fold factor for interspecies differences apparently is too small in order to cover the real variation. It was also noted that a general interspecies factor to cover all types of chemicals and all types of experimental animals cannot be expected. It was concluded that a 10-fold factor for interspecies variability probably protects a majority, but not all of the population, provided that the dose correction for differences in body size between experimental animals and humans is performed by the body surface area approach (Section 5.3.2.2). If the dose correction is based on the body weight approach (Section 5.3.2.1), the 10-fold factor was considered to be too small in most cases. 

The approach to exposure assessment is not as internationally harmonized as hazard assessment. A synopsis of current activities regarding exposure assessment for industrial chemicals in a number of OECD Member countries has been published (OECD 2006). The executive summary of this document states that while there is a significant level of sharing of approaches used for hazard characterization for risk assessment, this is not the case for exposure characterization. Although broad consistency in the overall approaches used by different countries in conducting exposure assessment exists, there is variation in policy-related factors, including the regulatory context for assessment and the way that information is applied, as well as in the types of approaches and tools used. 

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