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Market Report: Health & Safety pt2: Hand arm vibration, noise & dust Breathe more easily Many of the threats posed by dust are invisible. Nigel Strickland discusses the nature of the risks and some of the solutions that hirers can offer. For many years it has been known that dust generated during quarrying, mining and construction can cause respiratory problems for workers. In the UK today, awareness of the need for dust prevention and control is increasingly evident, with government air quality strategies and revised Health & Safety legislation changing attitudes and influencing work practices. In London and other major cities, fine particles of dust under 10 microns in diameter (referred to as PM10) generated by construction and other activities are recognised as significant pollutants. They could travel long distances, even in light winds, and could harm the health of the local population as well as site workers. The UK Air Quality Strategy requires local authorities to work towards achieving national air quality objectives. Accordingly, construction site operators are increasingly required to demonstrate that nuisance dust and fine particle emissions are effectively controlled to within acceptable limits. In addition, changes to the Control of Substances Hazardous to Health Regulations 1988 (CoSHH) were introduced in October 2006. Research suggested that the previous regulations permitted worker exposure to respirable crystalline silica (RCS) levels that gave rise to a 20% risk of contracting the debilitating illness, silicosis. There are 140,000 construction workers who are exposed to RCS on a regular basis. The new Working Exposure Limit (WEL) is now 0.1 milligrams of RCS per cubic metre of air, averaged over an eight-hour period (expressed as 0.1 mg/m3). This is almost impossible to visualise, but a sugar cube weighs approximately 3.75g, a milligram is one thousandth of a gram and 0.1mg is one tenth of a milligram! So the new WEL allows an incredibly small amount of RCS to be present. Silica dust can be created when building materials such as bricks, blocks, tiles and natural stone are subject to cutting, drilling and grinding.The visible particles are not the most harmful, as most are trapped in the nose and throat when inhaled. But the invisible RCS particles are inhaled deep into the lungs, potentially leading to serious illnesses such as silicosis and lung cancer. Effects of prolonged exposure can be latent for up to 20 years, by which time the results are irreversible and can be fatal. RCS can also cause chronic obstructive pulmonary disease (COPD), chronic bronchitis and emphysema. Controlling exposure In complying with CoSHH, employers must assess the risk and then prevent or control exposure to RCS dust to the WEL or less. This should be achieved by measures other than respiratory protective equipment, (RPE) as far as is reasonably practicable. One of the most effective methods of reducing RCS is through the control, or capture, of dust at source through suppression or extraction. Water suppression is a tried and tested method, either by using a pressurised water container, or by a hose connected to mains water supply or a water tank. Both methods are particularly suitable when used with petrol cut-off saws and studies suggest a minimum water flow rate of about 0.5 litres/minute optimises dust suppression. Obviously, this mode of control is not compatible with most electric power tools, although specialised products are appearing. Effective disposal of the residual dust slurry also needs to be considered. If it is left to dry it can be disturbed by later site activity and become potentially hazardous. One solution is to use wet suction vacuums. Capturing
dust
at
source,
using
mobile
dust
extraction
systems
(local
exhaust
ventilation,
or
LEV)
has
been
common
in
Europe
for
many
years
and
is
now
gaining
in
popularity
in
the
UK.
These
systems,
which
represent
an
obvious
hire
opportunity,
are
much
more
than
high-powered
vacuum
cleaners
and
the
basic
technology
needs
to
be
understood
by
users
and
hirers
alike.
A
European
standard
EN60335
classifies
LEV
systems
as
L,
M
or
H
(low,
medium
or
high
extraction)
and
it
is
vitally
important
to
recognise
that
the
size
and
capacity
of
the
system
must
match
the
task
in
hand.
The key component of any LEV dust extraction system will be the final element of its filtration system, known as HEPA (high efficiency particulate air filtration). The best can remove as much as 99.995% of airborne particles, including particles 0.3mg in diameter, which are the most harmful. The filters consist of a mat of randomly arranged fibres. It is commonly assumed that it acts like a sieve, whereby particles smaller than the largest opening can pass through, but this is quite wrong. HEPA filters target much smaller pollutants and particles, trapping them by interception, impaction or diffusion. Because of the extra density of the filter, the vacuum cleaner's motor needs to be more powerful to overcome the increased air resistance while still providing adequate cleaning power. These three elements combine to create the most effective method of ensuring that air exiting the vacuum meets the exposure limits. Most dust extraction systems also enhance worker safety by having a system of cleaning the pre-filter and emptying the collection bag, without exposing the operative to dust and ensuring the safe disposal of the contents. Capturing dust at source The
efficiency
of
dust
extraction
systems
can
be
further
enhanced
by
fitting
suction
casings
to
tools
such
as
grinders,
saws
and
drills
to
ensure
the
maximum
amount
of
dust
is
captured
at
source.
An additional method of controlling dust is by using mobile air cleaners which can be placed within an enclosed or screened work zone and continuously recycle air through a HEPA filtration system. These are particularly appropriate for refurbishment work in houses, schools, hospitals and offices, particularly where occupants are still resident. Finally, it is worth noting that it is not just our customers who are at risk from dust. Consideration needs to be given to hire industry technicians and mechanics, who daily repair and clean machinery returned from hire. It is inevitable that exposure to dust will occur, with minimal knowledge of the type, and the level, of dust. In the Nordic countries, where awareness of RCS issues has been evident for many years, hirers like Cramo have cleaning cabinets installed as a standard feature in their hire depot workshops. Tools and equipment are loaded on roller conveyors, through the end covers of the cabinet, which is connected to a central dust extraction vacuum. The technician can put his hands into the airtight cabinet and use an integral compressed air gun to clean the tool. With awareness of the health issues of dust rapidly increasing, it cannot be long before we see this type of solution commonplace in the UK. • Executive Hire News › Archives › April 2007 › Market Report › Breathe more easily
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