Health and Safety Briefing Note 2006-2

NEW WORKPLACE EXPOSURE LIMIT FOR RESPIRABLE CRYSTALLINE SILICA

Crystalline Silica

Crystalline silica is a solid substance (also known as quartz) found almost everywhere in the earth's crust. It is present in varying amounts in sand, which is widely used throughout the foundry industry. Crystalline silica (derived from sand) can be given off from various FOUNDRY processes and is fine enough to be inhaled into the lungs, the term used being "respirable".

What is the key health hazard?

The key health hazard from exposure to respirable crystalline silica (RCS) dust is silicosis.  Silicosis is a lung disease in which small hard nodules of scar tissue develop in the lungs. The nodules can be seen on chest X-ray. Silicosis can take some years to develop, and even after exposure to RCS dust stops it can get progressively worse. The main symptoms in affected people are difficulty in breathing and cough.  In severe cases it can lead to a shortening of life expectancy. Long-term exposures to high levels of RCS dust can also lead to an increased risk of developing lung cancer.

How does it get into the body?

RCS enters the body by breathing in the dust through the nose and mouth. Once it is inhaled, RCS dust can be retained in the lungs for many years.

Requirements of the COSHH Regulations

The Control of Substances Hazardous to Health Regulations (COSHH) are designed to ensure that the exposure of people at work to substances which could cause health damage is either prevented or, where that is not reasonably practicable, adequately controlled.  Employers are required to make an assessment of the health risk created by such work, and to prevent or control exposure to the substances involved.  The COSHH Regulations also require that persons who could be exposed to substances hazardous to health receive suitable and sufficient information, instruction and training.  Employers must therefore ensure that the requirements of the COSHH Regulations are fulfilled before allowing employees to undertake any procedure described in this MDHS.

Exposure Limits

The Workplace Exposure Limit (WEL) as listed in the current EH40/2005 workplace exposure limits is 0.3 mg.m-3. 

However, current evidence indicates that if workers are exposed regularly to 0.3 mg.m-3 there is a much higher risk of lung damage than had been previously thought.  As long term exposures to RCS can lead to an increased risk of developing lung cancer, the legal requirement is to control exposure as far below the WEL as is reasonably practicable. 

In the past some industry sectors had difficulty in controlling exposure below 0.3 mg.m-3. HSE believes it should now be reasonably practicable for all industry sectors to control to 0.1 mg.m-3 (8-hour TWA).

As such from the 1st October 2006, a new WEL of 0.1 mg.m-3 is  introduced and will be implemented by an amendment to HSE’s booklet EH40/2005 workplace exposure limits.

There is therefore a duty to control exposure to at least 0.1 mg.m-3, but also to as far below 0.1 mg.m-3 as is reasonably practicable using the HSE hiaracy of elimination (process substitution/change or engineering controls).

What foundries have to do

If exposure cannot be controlled to 0.1 mg.m-3 (8-hour TWA) or below by elimination, process change or engineering controls, then exposure must be controlled by provision and use of suitable respiratory protective equipment.  It must be remembered that the use of suitable respiratory protection must only be used as a last resort.

In dealing with exposure you should try to reduce the number of people exposed to RCS dust and the length of time each is exposed as required by good hygiene practice.

You must give all your employees who are, or who may be, exposed to RCS dust sufficient information, instruction and training to understand the potential problems and the precautions they need to take.

All  employees, safety representatives or representatives of employee safety must be aware of this information and be consulted on any action that you propose to take.

Many foundries already undertake monitoring for exposure to respirable silica on a regular basis as required by the COSHH regulations, and therefore are aware of the levels that their employees are exposed to, and are in a position to take action to reduce levels of exposure. 

Those foundries not undertaking such monitoring surveys must consider doing so, at least on one occasion to see if they have a problem, and then on a regular basis should personal exposures to RCS prove to be at a level where there is cause for concern, i.e. above half of the new WEL of 0.1 mg.m-3.

It should also be noted that the HSE are currently focusing on health in the foundry industry, and one of their major concerns is exposure to RCS.

Should any foundries have any questions regarding the information in this briefing note, or the need to discuss any monitoring requirements, please call Chris Mills at Cti on 0114 2537856 or email at c.mills@castingstechnology.com.

Chris Mills
Senior Consultant: Occupational Hygiene

19th October 2006