How and why we assess risk

What is risk?

Risk is a measure of the likelihood of harm to human health or the environment from exposure to an industrial chemical.

Risk is a function of both a chemical's innate hazards and the level of human or environmental exposure to that chemical. A chemical may be very hazardous but, if nothing is exposed to it, then the risk is low.

How we assess risk

To assess risk, we consider:

• the hazards of a chemical (the harm it is capable of causing)
• how humans and the environment will be exposed to the chemical

Staff in the Department of Health and Aged Care work on human health aspects and staff in the Department of Climate Change, Energy, the Environment and Water (DCCEEW), work on environmental aspects to assess:

• the level of risk from introducing and using chemicals
• how to manage the risks to promote the safe use of industrial chemicals

The length and complexity of the work depends on the issues involved and the scope of the assessment.

We use an approach that considers hazards and exposure scenarios in line with international best practice. There are several steps involved:

1. We consider the ways the chemical will be used, which then defines the scope of our risk assessment.
2. We identify what hazards are relevant for the chemical.
3. We characterise the hazards, which involves determining how the hazards and their severity vary with different levels of exposure.
4. We identify exposure scenarios and levels of exposure.
5. We characterise risks based on this work.

Assessing hazards

To assess hazards, we consider specific responses or effects called hazard endpoints. We use standardised endpoints that are internationally accepted as adequately exploring a range of possible adverse effects. Because they're standardised, we can share with and accept results from other regulators.

To assess relevant chemical hazards, we usually complete 2 stages of work:

• hazard identification
• hazard characterisation

To identify hazards, we consider information from many sources, including studies commissioned by industry, information from other regulatory bodies and public scientific literature. Most of our information is from overseas sources.

For human health hazards, sources of information include:

• in vivo (‘within life’) studies on whole animals
• in vitro (‘within glass’) studies on microorganisms, cells or biological molecules outside their normal biological context
• ex vivo (‘out of life’) studies in or on tissues from an organism in an external environment with minimal alteration of natural conditions
• in chemico (‘within chemical’) studies with simple chemicals that mimic biological molecules.
• in silico (‘within silicon’) studies using mathematical computer models to predict toxicity
• human epidemiological surveys, case reports or, in limited cases, controlled exposures in volunteers where the mechanisms of toxicity have been characterised so that tests can be conducted safely

For environmental hazards, sources includes:

• in vivo studies on whole animals
• in silico studies using mathematical computer models to predict toxicity

Sometimes, human health and environmental risks are related. For example, human exposure can occur from contact with polluted water. In this case, adverse effects may be of concern for both human health and the environment.

When there are no data on a specific chemical, we can ‘read-across’ data from other chemicals that are structurally or functionally similar. Relying on chemical analogue data like this always requires robust scientific justification.

We also seek data about physicochemical and environmental fate properties. They let us predict certain hazards. For example, a highly acidic chemical would likely cause skin irritation, while chemicals that naturally partition to water in the environment would be a concern for aquatic organisms.

Assessing exposure

We make several distinctions when considering exposure:

• worker (occupational) exposure versus public (consumer) exposure
• intentional versus unintentional exposure
• direct versus indirect exposure

For example, applying cosmetics is a direct intentional exposure. Poisoning from environmental contamination is an indirect unintentional exposure.

We separately consider occupational and public exposure because the exposure routes (ingestion, inhalation, skin, eye or mucous membrane contact) can be very different. Public exposure also considers infants and young children, who are not part of the workforce.

Indirect exposure via the environment is more likely to be relevant for public exposures than occupational exposures due to workplace controls.

We look at the type, intensity, frequency and duration of exposure, including how:

• people and the environment absorb the chemical
• the chemical moves through people and the environment

If we don’t have information on how a chemical is used in Australia, we estimate exposure based on overseas data or default values for typical Australian use.

Exposure often, but not always, has the most uncertainty. For humans, considering exposure includes estimating human activities and exposure scenarios. This covers the distribution and fate of the chemical in the whole environment. Indirect exposures via the environment can be an additional or even major exposure pathway. Multiple exposure scenarios can exist for a particular chemical.

Humans may be exposed to chemicals through areas like the skin, respiratory system and digestive system. We assess how external exposure leads to internal exposure (the amount of chemical taken into the body), and if a chemical builds up in the body (bioaccumulation).

The environment may be exposed to chemicals released to different environmental compartments such as the air, water, soil and sediment. We assess:

• how exposure leads to an increased concentration of the chemical in the environment
• what organisms the chemical affects

Organisms include microbes, plants, invertebrates and vertebrates. Chemicals can bioaccumulate in organisms.

Our main considerations for determining the concentration of a chemical in the environment are:

• the volume introduced
• how it’s released into the environment
• the fate of the chemical in the environment after release

We can use a tiered approach to exposure assessment. Our first approach uses simple, conservative assumptions that overestimate exposure. If that assessment finds the risks are acceptable, we don’t make further refinements. If the risks are unacceptable, we do a more detailed assessment.

Assessing risk

We may conduct either a qualitative or quantitative risk assessment. This depends on the:

• issues
• scope
• complexity
• required outcomes
• available data

Our qualitative assessments categorise risk using terms like low and high. They rely on descriptive accounts of hazard, exposure scenarios and risk-management scenarios, and are usually conducted when we don’t have enough data to quantify levels of exposure.

When we have sufficient data, we aim to conduct quantitative risk assessments. These provide a numerical estimate of risk based on measured or modelled numerical data from hazard and exposure assessments.

To avoid a false sense of precision, our assessments always discuss variability and uncertainty. If needed, we do sensitivity analyses to show how varying the input assumptions to the risk estimate affects the magnitude of the estimate.

The available data and any assumptions made due to uncertainty always limit risk characterisation. To manage uncertainty we use realistic, conservative assumptions to protect human health and the environment.

Information for a risk assessment sometimes conflicts or is of varying quality. In that case, we assess the information and make decisions using our expert judgement and a weight-of-evidence approach. This approach examines both the quality and consistency of data.

Based on our risk assessment, we determine:

• if risk mitigation is required
• what form the mitigation should take

We may make recommendations to other agencies, including:

• Safe Work Australia (workplace chemicals)
• Department of Health and Aged Care Advisory Committee on Chemicals Scheduling (consumer chemicals)
• ACCC (consumer chemicals and product safety)
• State/Territory bodies

Why we assess risk

We assess risk to work out if the introduction of an industrial chemical in Australia will adversely affect human health and the environment.

If an industrial chemical is to be introduced but isn’t listed on our Inventory, the introducer must categorise it to determine its risk level. We’ve created risk matrices combining hazard and exposure to help introducers do this.

There are 5 principles that guide our approach to risk assessment:

1. We focus our efforts based on likely risk so we use our resources well.
2. We follow international best practice and help develop methodologies and standards for risk assessment through international arrangements.
3. We are transparent. We disclose our approaches, uncertainties and assumptions. Anyone can read our assessments to find how we came to our conclusions and recommendations.
4. We aim to be realistic and conservative. We do this so we don’t underestimate risks. If essential data for a risk assessment are missing, we assume worst-case scenarios. Where possible, we use realistic worst-case scenarios. With these we aim to protect human health and the environment without excessive regulation.
5. We consult with risk management agencies to ensure our recommendations are targeted, practical and easily implemented.

What risks we assess

For human health, Department of Health and Aged Care staff consider:

• risks to workers
• risks to the public

For the environment, DCCEEW staff consider:

• risks to living organisms in air, water, soil, and sediment
• ecosystem impacts that can indirectly affect living organisms

We consider risks associated with 3 types of chemical hazards:

• Toxicological (adverse effects on humans)
• Ecotoxicological (adverse effects on ecosystems and environmental organisms)
• Physicochemical (adverse effects relating to the physical or chemical properties of the chemical)

We group human health endpoints into those that are:

• acute – occur from 1 or more exposures in a short time; chronic – repeated or continual exposure over a long time
• local – occur only at point of contact; systemic – within an organism away from the point of contact
• reversible – can be recovered from; irreversible – can cause permanent damage

This table covers typical human health endpoints.

Human health hazard endpoints

Hazard endpoint	Description
Acute toxicity	General adverse effects from: 1 exposure many exposures over a short period
Eye irritation/corrosion	Adverse changes to the eye from 1 exposure, for example tissue damage and decay of vision
Skin irritation/corrosion	Adverse changes to the skin from 1 exposure, for example rashes or ulcers
Skin and/or respiratory sensitisation	Allergic responses from several exposures via the skin or respiratory system
Repeated dose toxicity	General adverse effects from repeated or continual exposures over a long time
Mutagenicity and genotoxicity	Permanent, potentially inheritable changes in the amount or structure of human DNA
Reproductive and developmental toxicity	Adverse effects on: the function of sexual organs and structures fertility in human adult development of the embryo or foetus
Carcinogenicity	Effects related to inducing cancer

Environmental hazards consider organisms in air, water, soil and sediment as well as ecosystems. Environmental hazard endpoints focus on water because it’s the most likely destination for many chemicals entering the environment. Aquatic organisms absorb chemicals directly from the water, so they get more exposure compared with terrestrial organisms.

We typically consider 3 environmental hazard endpoints that represent 3 levels of the food chain in the aquatic ecosystem. Depending on the likely exposure scenarios, we also consider living organisms in air, soil and sediment. Our assessment answers the questions:

• How much of a chemical enters the environment?
• Where does it go?
• How long will it stay there?
• What organisms will be exposed?

This table covers typical environmental endpoints.

Environment hazard endpoints

Hazard endpoint	Description
Fish, acute toxicity	Adverse effects in an aquatic vertebrate from many exposures in a short period
Daphnia, acute immobilisation and reproduction	Adverse changes in behaviour and reproductive capacity of an aquatic invertebrate
Algal growth inhibition	Growth inhibition of fresh water microalgae (algae and cyanobacteria)