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consequence, the assessment of health and physicochemical risks are discussed separately in this chapter.

3.3 Things to consider in assessing health risks
The assessment of health risks from hazardous chemicals involves gaining an understanding of the situations where people can be exposed to, or come into contact with the chemicals, including the extent of exposure and how often this can occur. Health risk depends on hazard severity and level of exposure, and thus depends on both the type of chemical and also the nature of the work itself.
As with all risk assessments, the assessment involving chemical hazards needs to consider all workers potentially at risk, including those not directly involved in a work activity, as well as other people such as visitors to the workplace.

The routes of entry by which the chemical can affect your health
The type of hazard (for example, hazard classifications of carcinogenicity, sensitisation, acute toxicity) and relevant routes of exposure (for example, inhalation, ingestion, skin contact) should be known from the hazard identification step. These are needed in the risk assessment to understand the level of risk from likely or potential exposure scenarios in your workplace.
For particulates in air, the primary health concern is effects on the lungs due to inhalation exposure. For example, crystalline silica is considered hazardous principally because of the long term, irreversible lung effects (such as silicosis), that may arise from prolonged or repeated exposure to excessive concentrations. Its hazardous properties are associated with inhalation,
so the evaluation of risk should be based on the potential for breathing in the crystalline silica
dust rather than other routes of exposure (for example, contact with the skin). In the case of crystalline silica, it is the respirable fraction of the dust that presents the greatest risk to workers
as this fraction contains the smallest particles which can reach further into the lungs causing the most damage.
In contrast, even brief exposures to high concentrations of sodium hydroxide may lead to immediate effects which include irritation and burning of the skin, eyes and respiratory tract
and blindness. Its hazardous properties relate to exposure via skin or eye contact and inhalation. Evaluation of risks to health for sodium hydroxide (caustic soda) should therefore consider the potential exposure through all of these routes.
Some chemicals may exhibit ototoxic effects. That is, they may cause hearing loss or exacerbate the effects of noise. Evaluating the use of these chemicals should be carried out in conjunction with the Code of Practice: Managing Noise and Preventing Hearing Loss at Work.

The physical form and concentration
Some substances may be virtually harmless in some forms (such as a block of metal, a piece
of wood or granulated solid