Evaluating the Risks of Hazardous Chemicals

This section lists selected sources of information related to the evaluation of chemicals, including methodologies for evaluating the risks of chemicals. This information may be of use to countries in developing their own capacities to evaluate the risks associated with the use of hazardous chemicals and/or to better understand the processes followed at the international level in preparing evaluations of individual chemicals or groups of chemicals.

a) The WHO Recommended Classification of Pesticides by Hazard (2004)

This document sets out a classification system which distinguishes between the more and the less hazardous forms of selected pesticides based on acute risk to human health (i.e.the risk of single or multiple exposures over a relatively short period of time). It takes into consideration the toxicity of the technical compound and its common formulations.

The main section of the classification consists of five tables which separate technical grade active ingredients into the three classes listed below. A further table lists active ingredients unlikely to present acute hazard in normal use:

  • Extremely hazardous (Class Ia)
  • Highly hazardous (Class Ib)
  • Moderately hazardous (Class II)
  • Slightly hazardous (Class III)



b) Listing of WHO/IPCS publications and projects on risk assessment methodology

The World Health Organization's International Programme on Chemical Safety (IPCS) develops information and guidance on risk assessment methodologies. These aim to promote the development, harmonization and use of generally acceptable, scientifically sound methodologies for the evaluation of risks to human health and the environment from exposure to chemicals. The results of such work enhance mutual acceptance of risk assessment products.
The publications are available at: www.who.int/ipcs/publications/ehc/methodology_alphabetical/en/index.html
and on the INCHEM database at: www.inchem.org/

A selection of these guidance documents (listed below) may be downloaded here:

  • Human Exposure Assessment (EHC 214-2000)

    This monograph presents in one publication the concepts, rationale, and statistical and procedural methodologies for human exposure assessment. It presents the methodologies for surveying exposures, analyzing data and integrating findings with the ongoing national and global debate defining natural limits to human behaviour. The underpinnings/basis of exposure assessment are the environmental and biological measurements found in the more familiar specialties of air and water pollution and food and soil sciences. Therefore, throughout the document readers are referred to other publications for technical details on instrumental and laboratory methods. This monograph is intended for the community of scientific investigators enquiring about the human health consequences of contaminants in the environment and for those professions involved in devising, evaluating and implementing policy with respect to managing the quality of environmental health.

    Environmental Health Criteria 214 (2000)

  • Principles for the Assessment of Risks to Human Health from Exposure to Chemicals (EHC 210 - 1999)

    This monograph divides the risk assessment process into four distinct steps: hazard identification, dose-response assessment, exposure assessment and risk characterization. It outlines the nature of the data available and their use in the assessment of risk within a risk assessment/risk management framework. It is intended to assist in the interpretation of risk assessments on specific chemicals. The reader is referred to sources of chemical-specific hazard identification. Since exposure will vary considerably under different circumstances, responsible authorities are strongly encouraged to characterize risk on the basis of local measured or predicted exposure scenarios. The general approaches to exposure assessment described in this monograph will assist in characterizing risk in specific situations.

    Environmental Health Criteria 210

  • Assessing human health risks of chemicals: derivation of guidance values for health-based exposure limits (EHC 170 - 1994)

    This monograph explains how the guidance values for exposure to chemicals in environmental media in IPCS Environmental Health Criteria (EHC) monographs are developed and how they can be modified by national and local authorities in their development of limits and standards for environmental media.

    Environmental Health Criteria 170

  • Principles for Evaluating Health Risks to Reproduction Associated with Exposure to Chemicals (EHC 225 - 2001)

    This monograph summarizes current scientific knowledge on hazard identification and risk assessment for reproductive toxicity. Reproductive toxicity includes adverse effects on sexual function and fertility in males and females as well as developmental toxicity. This monograph is intended as a tool for use by public health officials, research and regulatory scientists and risk managers. It seeks to provide a scientific framework for the use and interpretation of reproductive toxicity data from human and animal studies. It also discusses emerging methodology and testing strategy in reproductive toxicity.

    Environmental Health Criteria 225

  • Principles for Evaluating Health Risks in Children Associated with Exposures to Chemicals (EHC 237 - 2006)

    This document provides a systematic analysis of the scientific principles to be considered in assessing health risks to children from environmental chemical exposures during distinct stages of development. The central focus of the document is on the child rather than on a specific environmental agent, target organ or disease. Thus it addresses the difficult task of integrating all that is known about exposure, toxicity and health outcomes at different life stages. The results of illustrative pollutants are described to demonstrate how exposure patterns, susceptibilities and mechanisms of toxicity change at different life stages and how these changes can impact on risk assessments. References are provided for more detailed information on environmental threats to children.

    Environmental Health Criteria 237

  • Approaches to Integrated Risk Assessments (ILO/UNEP/WHO/IPCS - 2001)

    This document provides a common framework for integrated risk assessments. Integrated risk assessments are defined as a science-based approach that combines the processes of risk estimation for humans, biota and natural resources in one assessment. The paper provides a framework for the integration of health and ecological assessments and is complemented by a series of illustrative case studies including, among others, POPs in humans and wildlife and organophosphorus pesticides in the environment.

    Integrated Risk Assessment


c) OECD Guidelines for the Testing of Chemicals

The OECD guidelines are a collection of internationally agreed test methods used by government, industry and independent laboratories to determine the safety of chemicals and chemical preparations, including pesticides and industrial chemicals. They cover tests for the physico-chemical properties of chemicals, human health effects, environmental effects, and degradation and accumulation in the environment.

These are the guidelines generally employed in developing scientific data concerning effects on human health and the environment submitted to regulatory authorities in support of the regulation of industrial chemicals or pesticides.