Public health assessment

Last update 17 August 2017

In broad terms, public health assessment aims to establish if there is potential for the chemical to adversely affect public health. This is influenced by two main factors: the nature and extent of public exposure to the chemical; and the chemical's toxicological properties.

Public exposure assessment

When assessing exposure, we begin by identifying the chemical, together with its estimated production or import volume and proposed use—examining its life history and considering the potential for the public to become exposed to it at each phase of its lifecycle.

This normally begins by assessing importation or synthesis and transport within the country. The assessment proceeds through to reformulation or use in industrial processes and possible use in consumer or industrial goods, and ends with the eventual disposal of the chemical (or products containing it).

Public exposure to notified chemicals most often occurs when they are sold in consumer products, or when products containing them enter the public domain.

The extent of public exposure depends on the concentration of the chemical in products, sales volume, pattern of use and other factors, including the physical state of the notified chemical.

We differentiate between the number of people likely to be exposed and the likely dose (amount of chemical) to which each person is exposed from the product's intended use.

Most members of the public will be exposed to a chemical constituent of a widely used product (for example, an additive to motor oil) but the amount of exposure may be minimised by the short time they are exposed to it and/or low frequency of contact.

Conversely, small numbers of people (for example, users of an exclusive small volume cosmetic or perfume), may be exposed to comparatively greater amounts of a chemical, with exposure increasing by prolonged or frequent contact.

Some products, such as ink cartridges, are packaged to reduce contact with the notified chemical during normal handling. Others may come into contact with the public without causing exposure. Polymers or dyes used in plastic or fibre, for example, may enter the public domain in an encapsulated, bonded or cured state from which they cannot be absorbed or otherwise become bio-available. Here, even extensive or prolonged contact would lead to negligible exposure.

We must take into account the possibility of public exposure arising from chemical release into the environment during transport, manufacture, reformulation and end-use.

Among the most important factors here is the amount of chemical which may be released, the location of possible discharges or spills, the chemical's physical state when it enters the environment and the chemicals persistence and ability to bioaccumulate. These factors influence the probability of public contact with the chemical at the release site, or the chemical exhibiting mobility in the air, soil or water, which will, in turn, determine if it may be inhaled or enter the potable water supply or food chain.

Emergency containment, cleanup and disposal procedures in the Safety Data Sheets could play a significant part in mitigating the effects of an accidental release, and will be noted by NICNAS.

Similarly, the notified chemical may enter the environment following its disposal, or disposal of products containing it. The assessment report will include this likelihood.

Toxicological properties assessment

Where toxicology data have been provided, we will assess toxicology for the nature and severity of hazards.

Irrespective of the class of notification of a new chemical, the identity and concentration of hazardous impurities or residual monomers will be examined, and we will comment on the likely toxicological significance at the levels present in products entering the public domain.

Implications for public health

Using the above information, we will assess if the chemical is likely to pose significant risks to public health. The use, concentration and physical state of the chemical when it reaches the public domain are important for this part of the assessment.

Many notified chemicals have no adverse effect on public health, due to low potential for exposure and/or low toxicological hazard. However, where frequent or prolonged public exposure to the chemical is anticipated due to its presence in consumer goods (for example, in cosmetics and personal care products), we may make a quantitative estimate of the user's exposure and systemic intake through repeated use.

Some applicants may supply exposure information but, alternatively, we may apply an algorithm or default values based on those described in the European Commission's Risk Assessment of Existing Substances [pdf]. Other sources of default values include those used by the Scientific Committee on Consumer Products.

The software package ConsExpo (Consumer Exposure and Uptake Models), developed by the National Institute for Public Health and the Environment (RIVM) in the Netherlands—and also included in the European Union System for Evaluation of Substances software—is based on the basic algorithms from the Technical Guidance Document. The default values contained in ConsExpo were mainly derived from European studies. This software package may alternatively be used for estimating consumer exposures.

In the absence of dermal absorption data for the notified chemical, a default dermal absorption value will be used to estimate systemic exposure, based on physicochemical properties.

The estimated systemic exposure is then compared with the NOAEL established in a relevant repeat dose toxicity study for the notified chemical to determine the margin of exposure between the anticipated consumer use and doses causing toxicologically significant effects in animals.

Finally, we will recommend whether special conditions are required to protect public health, such as placing warning statements on labels or establishing an upper limit to the concentration at which the notified chemical may be used in certain products.

Methods for Priority Existing Chemicals

Public health assessment methods for PECs are similar to those for new chemical notifications, but the assessment report may be larger and more complex, depending on the amount of information available on use and the extent of animal and human toxicological data.

If a survey of the PECs use in industrial and consumer products has been performed, we will use these results during assessment.

Where a PEC has been subjected to poisons scheduling (SUSMP), we may examine consumer product labels to verify compliance with the requirements of the schedule with regard to signal headings, first aid instructions and safety directions. Otherwise, we will comment on the general suitability of label directions and other statements.

If there is indication of potentially significant public exposure to the PEC, either from environmental sources or its use in, or contamination of, consumer products, we will assess the level of risk to the public. The approach taken will vary with the extent of data on exposure levels and toxicology, and with the nature of any hazard the PEC poses. A margin of exposure will then be calculated. Alternatively, the level of risk to the public may be determined from the extent of public exposure and epidemiological evidence of health effects in persons exposed occupationally.

Whenever there appears to be significant risk to public health, we make recommendations to reduce public exposure to the PEC.

Where public exposure arises from environmental contamination, we may recommend that measures be taken to reduce PEC emissions.

If the primary source of public exposure is from consumer products, we may recommend that the poisons scheduling status of the PEC be reviewed, or  that label instructions for use, first aid instructions and/or safety directions be revised.

Where the nature of the hazard or the level of risk requires it, we may recommend an upper limit to PEC concentration in consumer products, or even that PEC use in consumer products must stop.

Where there are concerns based on toxicological findings, but insufficient information on which to base realistic estimates of public exposure and risk, we may recommend that further data be obtained to enable a more adequate assessment.

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