Scrutinizing ACGIH risk assessments: the trichloroethylene case

Comparing in vivo, in vitro and in silico methods and integrated strategies for chemical assessment: problems and prospects

The RAINBOW workshop addressed the background for the integration of in vivo, in vitro and computer-based (in silico) methods, to facilitate the study of the toxic properties of chemicals. On the basis of these discussions, we prepared the present paper, outlining the strengths, weaknesses, opportunities and threats of each approach, both alone and integrated into a single testing strategy. The current scheme for evaluation of chemicals needs to be reshaped, in the face of the much larger numbers of chemicals which need to be examined and the availability of a diversified set of tools.

Science and Policy in Risk Assessments of Chlorinated Ethenes

In this article the use of data obtained from standardized experimental methods, for example, as specified in OECD guidelines for the testing of chemicals, epidemiology data, and mechanism data obtained from nonstandardized experimental methods in carcinogen risk assessment is scrutinized using the most recent risk assessments made by International Agency for Research on Cancer (IARC), the MAK(MAK)-Kommission, World Health Organization (WHO), European Centre for Ecotoxicology and Toxicology of Chemicals (ECETOC), and American Conference of Governmental Industrial Hygienists (ACGIH) for the four chlorinated ethenes as examples. The analysis shows that there was little controversy among these risk assessors about the interpretation of standardized animal data. On the other hand, they differ in their interpretation of epidemiology data, in particular in their assessment of statistical significance including the use of meta-analyses, and in quality evaluation of studies initiated on the basis of a priori concerns for carcinogenicity. The selection of mechanism data for species extrapolation is diverse among these risk assessors. Furthermore, in some cases they refrain from transparently motivating significant claims about mechanisms of toxicity by avoiding to give (explicit) references to the sources of information forming the basis of these claims or conclusions. This practice is not according to the scientific standards that should be required of a risk assessment document, and it makes it difficult to follow the argumentation and consequently to scrutinize the scientific accuracy of the conclusions drawn. In this article it is concluded that in some of these risk assessment documents, the use of mechanism data is not according to the scientific standards that should be required. It is furthermore concluded that if the use of mechanism data in these documents are representative of risk assessments in general, then there is an urgent need for further development and implementation of quality criteria for the use of mechanism data in species extrapolation.

Principles and practices of health risk assessment under current EU regulations

Risk assessments serve as the foundation of regulatory decision-making on whether to take actions to reduce (or otherwise manage) a toxicological or ecotoxicological risk or not. To understand the complex process that leads from the generation of scientific data, via risk assessment to risk management decision-making, close studies of the scientific basis and risk assessment methods must be undertaken. This paper consists of two main parts. In the first part the principles of the European Union process for risk assessments, as defined by legislations and official guidelines, are briefly outlined. In the second part the actual workings of this system are exemplified by the results from case studies of the risk assessment processes for trichloroethylene and for acrylamide. The analysis and comparison of these two cases illustrates: (1) that generation of a large amount of data does not ensure consensus among risk assessors, (2) that controversy can regard different levels of detail, (3) that controversy can arise at different organizational and theoretical levels, (4) that risk assessments may be subject to (public) criticism even if the experts agree, and (5) that "scientific" controversies have a significant policy component.

Modeling of methyl isothiocyanate air concentrations associated with community illnesses following a metam-sodium sprinkler application

BACKGROUND

A series of illnesses occurred in Earlimart, CA on November 13, 1999 following a metam-sodium sprinkler application to a potato field on the southern edge of the town.

METHODS

Case information was obtained from direct interviews, from illness complaints filed with state or county agencies, or from illness reports filed by community physicians for 173 subjects. Air concentrations of the by-product methyl isothiocyanate (MITC) during the episode were estimated based upon the Industrial Source Complex Short-Term (ISC3) air dispersion model, estimates from prior metam-sodium monitoring studies, and data from weather stations in two adjoining communities.

RESULTS

Weather station data indicated that the November 13th incident corresponded with a temperature inversion at approximately 5:00 p.m. and a shift in the direction of prevailing wind from northwest to southeast. On the edge of Earlimart, 1-hr time weighted average (TWA) MITC concentration estimates ranged from 0.5 to 1 ppm. Of the 173 subjects, 170 had MITC-compatible symptoms, including eye or upper respiratory irritation (77.6%), non-specific systemic symptoms (64.7%), and lower respiratory symptoms (20.0%). 78.2% were exposed within 0.5 miles of the northern edge of the treated field where average 1 hr MITC concentrations exceeded the 800 ppb ocular irritation threshold.

CONCLUSIONS

ISC3 modeling is a useful means of evaluating MITC concentrations for illness episodes when industrial hygiene assessment is not possible.

Acrylamide and cancer risk—expert risk assessments and the public debate

This study has two parts. In the first part, fourteen carcinogen risk assessments of acrylamide made by different expert groups during the years 1976-2002 are compared in terms of their overall conclusions and their use of primary data. In the second part, the public debate on acrylamide and cancer risks and the questioning of the expert risk assessment, that arose as a reaction to the identification of this substance in staple food is discussed. In the first part it is shown that the expert risk assessors concur to a large degree about the assessment of the acrylamide potential to cause cancer. Three risk assessors have concluded that acrylamide is neither carcinogenic to humans nor to animals, while eleven risk assessors have concluded that acrylamide is carcinogenic in animals and is likely to be carcinogenic in humans. The differences in the overall conclusions seem to a large extent be explained by an evolving database. The risk assessors agree considerably on how to interpret and evaluate the available primary data, but the coverage of the available references is low. These results are also compared to those previously published on risk assessments of trichloroethylene. In the second part the arguments used in the public debate to question the expert risk assessment are summarized and it is argued that they are not based on the principles generally accepted in toxicological risk assessment.