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SAFE to BREATHE

Dust and fume control in the rubber industry

Contents

Introduction

This leaflet is aimed at both employers and employees. It provides practical guidance on effective dust and fume control in the rubber industry. This advice will help you to comply with your duties under the Control of Substances Hazardous to Health Regulations1 (COSHH) by helping you create a healthier working environment. However, this is only an introduction to the subject and further references are given at the back of the leaflet.

Health studies have shown an increased risk of cancer in workers employed in the stages of rubber processing which produce rubber dust and fume. Previously, certain known carcinogens have been successfully prohibited or substituted. For example the excess of bladder cancer in the industry has been eliminated by stopping the use of materials containing 2-naphthylamine and related chemicals. However you still need to be vigilant and maintain a high standard of dust and fume control.


Legal requirement

The Health and Safety at Work etc Act 1974 requires employers to provide and maintain working conditions that are safe and without risk to the health of employees, so far as is reasonably practicable.

The Safety Representatives and Safety Committees Regulations 1977 require employers to allow appointed safety representatives time off with pay for training so they can carry out their functions. Safety Representatives also have the right to be consulted over the planning and organisation of any health and safety training provided for those they represent.

Workplace Exposure Limits (WELs)

Employers also have duties under the Control of Substances Hazardous to Health Regulations 2002 (COSHH) to control risks to employees’ health arising from work activities.  This means they need to ensure exposures to dust is kept as far below the Workplace Exposure Limits (WELs) as reasonably practicable.

WELs are the concentrations of hazardous material in the air averaged over a specified time period – called the Time Weighted Average (TWA).

Two periods are used, long-term (8 hours) and short-term (15 mins) – the long-term representing a working day and the short-term to help prevent effects such as eye irritation which may occur after only a few minutes exposure.

The current WEL for rubber process dust is 6mg/m3 8 hour time weighted average.

The current WEL for rubber fume is 0.6mg/m3  8 hour time weighted average.

Rubber process dust

This is dust from rubber manufacture where ingredients are handled, weighed, added to or mixed with uncured natural or synthetic elastomers. It does not include dusts arising from the abrasion of cured rubber.

Rubber fume

This is fume from the mixing, milling and blending of natural rubber or synthetic elastomers. It is also fume from natural rubber and synthetic polymers combined with chemicals, and in the processes which convert the resultant blends into finished process dust products (or parts thereof). It also includes any inspection procedures where fume continues to be evolved.

Workplace exposure limits for individual chemical substances which may be present will also apply, for example carbon black, certain whitings and most common solvents2.


A strategy for dust and fume control

A systematic approach to the control of dust and fume is essential, otherwise individual approaches or solutions may conflict.

COSHH requires employers to:

Further guidance on complying with COSHH has been produced by HSE3.


Assessing the risks to health from dust and fume

To assess the risks from exposure to dust and fume you need answers to such questions as:

It is not enough to say that dust and fume is invisible under normal (and sometimes murky) lighting. Remember - dust which is normally invisible can still be harmful.

You will need to assess the extent of exposure to dust and fume to see if the controls are adequate. You may need to do air monitoring. You may be able to see dust releases invisible to the eye by using a bright light source (Tyndall beam) and use smoke tubes or a smoke generator to follow air currents.

Methods exist for measuring rubber fume and dust levels in air4,5. Personal samplers worn on workers' lapels, together with static samplers placed around the workrooms, give the most complete picture of dust and fume emissions and exposures.

This is detailed specialist work and may need to be carried out under the supervision of an experienced occupational hygienist. You have an important role in making sure that the sampling takes place for a representative proportion of the working shift under typical working conditions. The people who actually do the work and breathe the air also have a key role in helping with the assessment. Make sure that you consult them about the actual working methods adopted and the true representative nature of the sampling, and inform them of the results of the assessment.

Compare the results of air sampling with the relevant exposure limits, and guided by this information identify the areas where improved dust and fume control is needed.


Selection of control methods

Elimination and substitution

Your first priority should always be to consider whether you can prevent exposure to rubber process dust and fume.


Can you eliminate a particular substance or process? This has already been done in the industry with Nonox-S and NDPA.

Can you substitute a particular substance with one which is less hazardous, or use the same substance in a less hazardous form?

Consider using dust-suppressed materials, for example pellets, flakes, oil coated powders and polymer bound chemicals. Smithers RAPRA Technology Ltd6, The British Rubber Manufacturers' Association Ltd7 and chemical manufacturers can supply information concerning dust-suppressed chemicals, which are widely available.

Anti-tack powders can be substituted in many applications by water-based dispersions.

Containment

Enclosed processes are cleaner. Use of enclosed and automated bag and powder handling plant with direct feed to process machines, where practical, is cleaner than handling paper sacks, bins etc. Proprietary enclosed bag opening and disposal units fitted with local exhaust ventilation are also available.

Internal mixers and bulk powder handling plant have seals and joints which need good design, regular inspection and routine maintenance.

Process control

Significant reductions in fume levels may be achieved by avoiding compound temperatures in excess of process requirements. Fuming products should be cooled as soon as they have finished processing for example using water, air or by passing cured items over chilled surfaces. Alternatively they may be allowed to cool in an area controlled by ventilation. Flash and scrap from freshly moulded items can be quench cooled in cold water as a cheap and easy means of fume control.

You may also need to consider other factors in fume evolution, for example throughput and compound formulation.

Handling and working methods

Methods of work can significantly reduce dust and fume exposures. Make sure that employees are fully involved in designing and introducing new working methods.

Consider use of low melt compound compatible bags for small drugs, which are added direct to the mixer.

Avoid double handling of powders at the weighing stage ie weighing them into the weigh scale pan and then into the required container.

Sacks, bags etc should be opened, emptied, rolled up, and where possible disposed of, under local exhaust ventilation (LEV). Better still, consider the use of an automated delivery system.

Make sure that receptacles are properly designed and stationed so that workers do not have to bend into deep and dusty containers.

Cured products should preferably be trimmed when cool. If they must be worked on when still fuming, local exhaust ventilation control will be needed.

Ventilation control

Local exhaust ventilation (LEV) is widely applicable for controlling dust and fume. Before you consider modifying plant and equipment it is sensible to check the effectiveness of existing controls; in many cases relatively small expenditure on cleaning, adjustment, repair and general maintenance can improve the performance of a ventilation system.

3 basic steps to design and maintain effective local exhaust ventilation:

Assessing how exposure to dust and fume takes place, including how the job is done, is essential in designing an effective LEV system. It is important that the design around the workstation, including the hood or enclosure, is taken into account for the system to work properly. It takes experience and expertise to design and install an effective LEV system, so make sure that a competent and reliable firm is chosen. After installation, the LEV system must be commissioned to prove that effective control has been achieved. A commissioning report, manual and logbook should also be provided

Faulty and indifferent maintenance is a major cause of failure of ventilation systems. Regular checking  and maintenance is vital, both practically and commercially, and is also a requirement of COSHH.

Fitting air flow indicators will help to show that control continues to be maintained during use. A correctly calibrated airflow indicator is currently the only method that will show you immediately if there is a problem such as incorrect flow adjustment, blockage or damage to ducting.

LEV plant should be examined and tested at least once in every 14 months and the results recorded. The performance of such systems should be checked against design specifications as part of this maintenance schedule. In addition, it is recommended that LEV plant be checked weekly by a responsible person for signs of leaks and damage.

Other types of ventilation engineering can be effective, in appropriate circumstances, for the control of hot rubber fume at presses. However the application of such control methods is limited and the correct design is essential.

The quality and location of emissions of dust and fume to the atmosphere is covered by the Environmental Protection Act 19908. You should consult your local environmental health (or protection) officer for advice on this matter.

Segregation

By segregating dusty processes you can reduce the number of workers at risk. However, this is only a partial solution and should be used with other operational and engineering controls. This principle can also be applied to fume control. In some circumstances fuming freshly produced rubber can be moved away from the areas occupied by people into a separate ventilated area to cool.

Personal exposures can also be reduced by limiting the time spent close to dust and fume, for example by use of automatic feed and take-off devices at two-roll mills.


Common health hazards and control measures

Factory process Health hazard Control measures
Drug room Dust from 'small drugs' (complex organic compounds 1 Substitution 4 Dust-suppressed chemicals
2 Master batch 5 Local exhaust ventilation
3 Preweighed, sealed bags 6 Care in handling, including bag opening and disposal
Dust from bulk fillers and whitings 1 local exhaust ventilation 3 Automatic weighing and direct feed into mixer
2 Care in handling, including bag opening and disposal
Dust from carbon black 1 Master batches 3 Automatic weighing and direct feed into mixer
2 Local exhaust ventilation
Skin contact with process oils 1 Direct metering into mixer 2 Good skin protection and skin care
Compounding Dust 1 local exhaust ventilation 4 Dust-suppressed chemicals
2 Master batches 5 Direct feed into mixer
3 Preweighed, sealed bags 6 Care in handling, including bag disposal
Fume 1 local exhaust ventilation 3 Process temperature control
2 Cool hot products quickly, or removet o ventilated area to cool
Skin contact with process oils 1 Direct metering 3 Good skin protection and skin care
2 Care in handling
Moulding/curing Fume 1 Local exhaust ventilation at presses; autoclave doors; workstations for trimming; and/or storage racks 5 Allow autoclave to cool before opening
2 Effective general ventilation 6 Products cool before handling; flash cooling of scrap and sprue
3 Control over processing temperature 7 Segregation - deflecting fume upwards using screens
4 Cool hot products quickly, or remove to ventilated area to cool; automated product removal to conveyors
Calendering andextrusion Fume 1 Local exhaust ventilation 3 Control over processing temperature
2 Direct or indirect water cooling of product
Dust from release agents (chalk, stearate, talc) 1 Substitution by wet methods 2 Enclosure and local exhaust ventilation

The following points are important:

Housekeeping and cleanliness

You can reduce dust levels in working areas by maintaining a good standard of housekeeping and cleanliness.

A regular and efficient cleaning programme on every shift to remove the deposits of dust on floors, ledges and machine casings is essential. Use vacuum cleaners rather than brushes which raise clouds of dust. For most materials handled in drug rooms a type H industrial vacuum cleaner for dusts hazardous to health will be appropriate9.

Respirators

Respirators should not be necessary if effective dust and fume control measures have been applied and should only be considered as a last resort. However they may be needed for short-term exposures, eg filter bag changing and general maintenance, or when urgent action is required due to failure of plant. It is essential that the correct respirator is chosen for the type and level of dust or fume likely to be present. The respirator should be acceptable and suited to the wearer and be properly maintained. Under COSHH, respirators (other than disposable types) should also be thoroughly examined and where appropriate tested. This should be at least at monthly intervals.

Wearers of tight fitting respirators need to be face fit tested either by a qualitative or a quantitative test.  Tight fitting respirators are not suitable for wearers with facial hair.

Training of workers in the use and maintenance of respirators is essential10, and should include the following:


Control strategy

A combination of engineering, technical and operational control measures, coupled with appropriate training and instruction of employees involved, should form the basis of an effective strategy for dust and fume control. The table on pages 8 and 9 provides a summary. More advice on dust and fume control can be found in Fume from rubber presses11 and Controlling airborne contaminates at work12.

This is a complex, dynamic and competitive industry; formulations and process conditions are always changing. New formulations and higher temperatures may introduce new risks and improved research techniques may reveal the dangers present in old established processes.

Employers should review their assessment of the risk and the adequacy of controls on a regular basis and improve dust and fume control further where necessary. If there is reason to think that the assessment is no longer valid or there has been a significant change in the work, this should be done straight away. Employees and safety representatives should assist and co-operate with employers to make sure that their environment is safe and healthy, and that control measures provided for their protection are adequately maintained, properly used and that problems with them are reported to their employer promptly.


References

The following publications referred to in the text offer further practical advice on the assessment and control of dust and fume in the rubber industry:

  1. Control of Substances Hazardous to Health (Fifth edition) Control of Substances Hazardous to Health Regulations 2002 (as amended) Approved Codes of Practice and guidance L5 ISBN 0-7176-2981-3
  2. EH40/2005 Workplace exposure limits – Containing a list of workplace exposure limits for use with the Control of Substances hazardous to Health regulations 2002 (as amended) ISBN 0-7176-2977-5
  3. See the HSE COSHH website http://www.hse.gov.uk/coshh/index.htm
  4. MDHS 47/2 Methods for the Determination of Hazardous Substances in Air Health and Safety Laboratory - Determination of rubber process dust and rubber fume (measured as cyclohexane- soluble material) in air) - Laboratory method using filters, gravimetric determination and soxhlet extraction - 1999, ISBN 0-7176-2419-6
  5. Methods for the Determination of Hazardous Substances in Air No 14: General methods for the gravimetric determination of respirable and total inhalable dust MDHS 14 HSE Books 2000
  6. Smithers Rapra Technology Limited, Shawbury, Shrewsbury, Shropshire, SY4 4NR http://www.rapra.net/contact.asp
  7. Toxicity and safety handling of rubber chemicals (4th edition) 1999 Rapra Technology and BRMA Code of Practice ISBN 978-1-85957-174-3. This Code of Practice provides a detailed review of rubber chemicals in use together with available information on hazardous properties likely to be of concern to the user. It is widely accepted as the standard reference work on rubber chemicals.
  8. Environmental Protection Act 1990: Environmental Protection (Prescribed Processes and Substances) Regulations 1991 (SI 1991/472); and related Regulations.
  9. BS EN 60335-2-69:2009 Household and similar electrical appliances – Safety – Part 2-69: Particular requirements for wet and dry vacuum cleaners, including power brush for commercial use
  10. Respiratory protective equipment at work: A practical guide HSE Books HSG 53 2005 ISBN 0-7176-2904-X
  11. Fume from rubber presses (smaller articles) RB05
    http://www.coshh-essentials.org.uk/assets/live/rb05.pdf
  12. Controlling airborne contaminants at work – A guide to Local Exhaust Ventilation (LEV) HSG 258, ISBN 9-7807-1766-2982

How to obtain HSC/E publications

HSE publications are available from HSE Books at http://books.hse.gov.uk/hse/public/home.jsf

British Standards can be purchased from the BSI online shop at http://shop.bsigroup.com

This leaflet was originally prepared by the Rubber Industry Advisory Committee and was also agreed by the Health and Safety Commission. It contains notes on good practice which are not compulsory but which you may find helpful in considering what you need to do.

This publication may be freely reproduced, except for advertising, endorsement or commercial purposes. The information was updated 7/2011. Please acknowledge the source as HSE.

2013-06-20