SAFE to BREATHE
Dust and fume control in the rubber industry
Contents
- Introduction
- Legal requirements
- Occupational exposure limits for dust and fume
- A strategy for dust and fume control
- Assessing the risks to health from dust and fume
- Selection of control methods
- Common health hazards and control measures
- Control strategy
- References
- Further reading
- How to obtain hse/hsc publications
Introduction
This leaflet provides outline practical guidance on effective dust and fume control for both employers and employees in the rubber industry, and is based on current good practice. Following the advice in this leaflet will lead to a healthier working environment and will help you to comply with your duties under the Control of Substances Hazardous to Health Regulations1 (COSHH). This is only an introduction to the subject; sources of further advice 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 process dust and fume. In the past, certain known carcinogens have been successfully prohibited or substituted - for example the excess of bladder cancer in the industry has been eliminated by discontinuing 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 at rubber industry processes.
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. COSHH1 expands on this general duty and requires employers to prevent worker exposure to hazardous substances or, where this is not reasonably practicable, to ensure adequate control. Employees are required to make full and proper use of the control measures provided and to report any defects in them promptly to their employer.
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.
Occupational exposure limits for dust and fume
Maximum Exposure Limits (MELs)
- COSHH requires that workers' exposure to rubber process dust and rubber fume must not exceed, and should be reduced as far below the MELs as is reasonably practicable.
- rubber process dust 6mg/m3 8 hour time weighted average
- rubber fume 0.6mg/m3 8 hour time weighted average
Rubber process dust
Dust arising in the stages of 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
Fume evolved in the mixing, milling and blending of natural rubber or synthetic elastomers, or of natural rubber and synthetic polymers combined with chemicals, and in the processes which convert the resultant blends into finished products or parts thereof, and including any inspection procedures where fume continues to be evolved.
Occupational 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:
- assess the risks to health caused by exposure to dust and fume in rubber processes;
- take steps to ensure that exposure is prevented, or failing that, adequately controlled;
- take steps to ensure that the rest of the requirements of COSHH are met.
Further guidance on complying with COSHH has been produced by HSE3 and by The Rubber Industry Advisory Committee (RUBIAC)4.
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:
- who is exposed and to what?
- to how much and for how long?
- from where?
- how is dust and fume controlled?
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 take samples of the air. You may be able to see dust releases using a bright light source or use smoke tubes to follow air currents.
Methods exist for measuring rubber fume and dust levels in air5,6. 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 chemical 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. RAPRA Technology Ltd14, The British Rubber Manufacturers' Association Ltd15 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).
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:
- identification of the nature and source of the dust and fume, in particular the method of generation
- competent design, installation and commissioning of the ventilation system
- regular inspection and maintenance.
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.
Faulty and indifferent maintenance is a major cause of failure of ventilation systems. Regular inspection and maintenance is vital, both practically and commercially, and is also a requirement of COSHH. 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 inspected 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 essential13.
The quality and location of emissions of dust and fume to the atmosphere is covered by the Environmental Protection Act 19907. 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, but this is only a partial solution and should be used in conjunction 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, eg 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 | 1 | Substitution | 4 | Dust-suppressed chemicals |
| organic compounds | 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 | opening and disposal | ||
| 2 | Care in handling, including bag | 3 | Automatic weighing and direct feed into mixer | ||
| 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 | to ventilated area to cool | ||
| 2 | Cool hot products quickly, or remove | 3 | Process temperature control | ||
| 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; | area to cool; automated product removal to conveyors | |
| 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 | ||
| 3 | Control over processing temperature | and sprue | |||
| 4 | Cool hot products quickly, or remove to ventilated | 7 | Segregation - deflecting fume upwards using screens | ||
| Calendering and | Fume | 1 | Local exhaust ventilation | 3 | Control over processing temperature |
| extrusion | 2 | Direct or indirect water cooling of product | |||
| Dust from release agents (chalk, | 1 | Substitution by wet methods | 2 | Enclosure and local exhaust ventilation | |
| stearate, talc) | |||||
Three general points are emphasised:
- Protective clothing, eg gloves, aprons, overalls, safety glasses/goggles, appropriate to the relevant conditions of handling should be worn and training given. A high standard of personal hygiene should be adopted and maintained. Adequate washing facilities should be provided
- Good housekeeping in powder handling areas is essential. Particular care is required in stacking, transporting, bag opening and bag disposal. Spillages should be cleaned up promptly using suitable vacuum cleaners
- Seperate mess areas should be provided for eating and drinking
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 appropriate8.
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, at regular intervals.
Training of workers in the use and maintenance of respirators is essential9,10.
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 detailed advice on dust and fume control at specific processes can be found in separate RUBIAC booklets.11,12,13
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: those marked with an asterisk pre-date the COSHH Regulations but still contain much useful information.
- Control of Substances Hazardous to Health and Control of Carcinogenic Substances Approved Codes of Practice, Control of Substances Hazardous to Health Regulations 1994 L5 HSE Books 1995 ISBN 0 7176 0819 0
- Guidance Note EH40 Occupational Exposure Limits (HSE publication revised annually) HSE Books (For 1995, EH40/95)
- A step by step guide to COSHH assessment HS(G)97 HSE Books 1993 ISBN 0 11 886379 7 This booklet sets out a step by step approach to carrying out a COSHH assessment. The principles of assessment are well illustrated with extensive examples from a range of industries.
- COSHH in the rubber industry (RUBIAC publication) HSE Books 1992 ISBN 0 11 885610 3 This booklet shows how the requirements under COSHH can be complied with as a package. Helpful examples specific to rubber industry processes are included.
- Methods for the Determination of Hazardous Substances in Air No 47: Rubber fume in air measured as 'total particulates' and 'cyclohexane soluble material' MDHS 47 HSE Books 1987 ISBN 0 11 885638 3
- 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 1993 ISBN 0 7176 0509 4
- Environmental Protection Act 1990: Environmental Protection (Prescribed Processes and Substances) Regulations 1991 (SI 1991/472); and related Regulations.
- BS5415: Section 2.2: 1986 Specification for vacuum cleaners, wet and/or dry Supplement No 1 (1986) to BS5415: Section 2.2: 1986 Specification for type H industrial vacuum cleaners for dusts hazardous to health BSI
- Respiratory protective equipment: A practical guide for users HSE Books 1990 ISBN 0 11 885522 0 This booklet provides information on the wide range of respiratory protective equipment available, including useful illustrations, and gives detailed advice on the selection of appropriate equipment. The importance of proper training and maintenance are emphasised.
- Grin and wear it IND(G) 137 L HSE Books 1993 This free leaflet is aimed at employees and answers some basic but important questions about use of respiratory protective equipment.
- Dust control in powder handling and weighing (RUBIAC publication) HSE Books 1989 ISBN 0 11 885495 X This well-illustrated booklet outlines practical strategies for controlling dust. Guidance is given on factors to consider when designing a local exhaust ventilation system; some illustrations show good and bad designs.
- Control of dust and fume at two-roll mills (under revision) (RUBIAC publication) HSE Books 1986 ISBN 0 11 883850 4 This RUBIAC booklet includes several useful illustrations of exhaust ventilation enclosures at two-roll mills, including those where conveyors need to be incorporated and mills worked from both sides. This booklet is in the process of being updated and expanded to cover internal mixers.
- Control of rubber fume at extruders, calenders and vulcanising operations (RUBIAC publication) HSE Books 1994 ISBN 0 7176 0783 6 This RUBIAC booklet contains straightforward, practical advice on a range of methods of fume control, including ventilation control but also aspects of rubber technology, process control and administrative controls.
- RAPRA Technology Ltd, Shawbury Road, Shrewsbury SY4 4NR
- The British Rubber Manufacturers' Association Ltd, Health Research Unit, Scala House, Holloway Circus, Birmingham B1 1EQ
Further reading
Toxicity and safety handling of rubber chemicals (3rd edition) 1990 BRMA Code of Practice ISBN 0 90311018 0
British Rubber Manufacturers Association publication. 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.
Introduction to local exhaust ventilation HS(G)37 (Rev) 1993 HSE Books ISBN 0 11 882134 2
The maintentance, examination and testing of local exhaust ventilation (HSE publication) HS(G)54 1990 HSE Books ISBN 0 11 885438 0
Respiratory protective equipment, legislative requirements and lists of HSE- approved and type-approved equipment 1992 HSE Books ISBN 0 11 886382 7
How to obtain HSC/E publications
HSE/HSC publications are available by mail order from HSE Books, PO Box 1999, Sudbury, Suffolk, CO10 6FS
Tel: 01787 881165
Fax: 0787 313995
HSE/HSC priced publications are also
available from all good booksellers.
Other enquiries should be directed to HSE's Information Centre, Broad Lane, Sheffield S3 7HQ
Tel: 0114 289 2345
Fax: 0114 289 2333
British Standards are available from 389
Chiswick High Road, London W4 9AL
Tel: 0181 996 7000
Fax: 0181 996 7001
This leaflet was prepared by the Rubber Industry Advisory Committee and has been 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 is current at 6/95. Please acknowledge the source as HSE.
IACL95 6/95 C120
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