Ultraviolet Process Hazards:
Ulraviolet (UV) curable inks, varnishes and lacquers are composed of liquid components which co-polymerize to a plastic solid when exposed to a high intensity UV light source. Less frequently, an electron beam (EB) is used. UV cured inks can effectively be considered solvent free, however solvents are still used for press wash-up. Health, safety and environmental precautions for both UV and EB cured processes are similar.
UV technology is important in the production of all types of printing and packaging applications where their fast drying, durable and high gloss finish make them suitable for immediate use. Many conventional printing machines cam be adapted to use UV inks, varnishes or lacquers. Separate varnishing attachments may also be adapted to UV. Applications include carton printing – including food and pharmaceutical packaging, labels, plastic substrates, and metal decorating. Some applications also involve EB technology, such as security printing, where thick film coatings are required.
Exposure to UV radiation, even limited, will cause acute, abnormal redness on normal skin. In certain people exposure to UV inks may result in skin sensitization – an allergic reaction that can manifest itself at any time in some people. For a sensitized person, further contact with the material concerned, even at very low doses, may cause a severe reaction. In most circumstances the condition is irreversible.
UV inks and varnishes as a result of the inclusion of substances to help the formulations or other physical properties of the inks in use may present certain other hazards. Suppliers are required to provide up to date material safety data sheets and to identify key hazards on product labels. Users should be sure they have up to date information on the products and have identified specific hazards before use.
How are workers exposed?
Contact with UV curable inks, varnishes, etc. may cause skin irritation or, in certain people, skin sensitization.
Inhalation of ink mist or fly: In some circumstance small ink droplets may become airborne. The mist formed presents a hazard from inhalation and may be irritating to the skin and respiratory tract. It can have the potential to cause respiratory sensitization.
Contact with wash up solvents: The effects of exposure to wash-up solvents depends on the type of solvent used, and can range from dermatitis to damage to the central nervous system. (See the Hazards Watch on solvents.)
Inhalation of ozone: Exposure to ozone gas can lead to eye, nose and throat irritation and at higher levels, headache, or nausea. At high levels chest pains and a cough may occur.
Exposure to UV Light: Exposure to direct UV light may irritate the eyes or burn the skin. It may also result in conjunctivitis, which is inflammation of the mucous membrane lining the inside of the eyelid and the forepart of the eyeball. Symptoms may be delayed several hours. Certain sensitive people may suffer retinal damage and people suffering from certain rare medical conditions or prescribed certain drugs may suffer an extreme reaction, for example an exaggerated sunburn reaction.
Exposure to electron beam (EB) energy: Exposure to electron beam energy can cause damage to the soft tissue and other organs.
How do you control worker exposure?
Consider elimination or substitution of products that present the highest risk to workers and the environment. Print employers should carry out a risk assessment and select the lowest risk product.
Machinery design and integrity: Normally users should expect to have temperature control for rollers and UV units. This may be achieved by means of water cooling and/or air cooling. This ensures consistent ink viscosity and helps to prevent ink misting. It also allows higher printing speeds and helps maintain quality. On some existing machines the only way to control ink misting may be to provide local exhaust ventilation (LEV) discharging to a safe place in accordance with local environmental considerations.
Reduce contact with solvents and inks:
- Adopt a high standard of personal hygiene and housekeeping, including regular cleaning of work areas and the use of high quality hand cleaners and skin moisturizers.
- Clothing providing protection for the arms and legs should be provided, worn and treated accordingly when contaminated. Work clothing should be stored separately from personal clothing and not taken home to launder.
- Preferably automatic wash-up facilities should be provided and used for press cleaning. Operators should be provided with and wear suitable gloves.
- Gloves of a length to overlap the sleeves of overalls should be used. In all circumstances gloves should be replaced when punctured or worn out.
- Waste materials such as wipes should be disposed of in a properly labeled, dedicated bin. A centrifugal dryer that extracts liquids has been developed so rags come out dry and all liquids are then collected and disposed of.
- A safe system of work should be adopted for clearing jams, including the provision of appropriate personal protective equipment (PPE) and workers trained in its use.
- If ink wash-up trays and other equipment are regularly removed from the machine for cleaning, then a suitable bench fitted with local exhaust ventilation and a disposal point for waste wipes may be considered appropriate.
- Where possible, automatic ink dosing should be investigated and used.
- Press cleaning should be performed using the least hazardous solvents available.
Eliminate exposure to direct UV light or ionizing radiation: Prevent exposure with proper screening and effective interlocking that switches off the UV or EB unit if the shields are opened.
Reduce exposure to ozone: Provide cold-cure quartz filtered UV curing units and/or exhaust ventilation to eliminate ozone from the working environment. Before exhausting to the environment appropriate treatment devices should be provided to accord with related legislation. In the case of cold cure quartz filtered UV curing units, where LEV is not generally provided, ozone levels should be assessed to ensure that the risk from ozone is adequately controlled. These checks should also be carried out if the equipment is substantially altered.
Provide health surveillance: Nominate a responsible person to perform checks of exposed areas of skin for skin disorders. Promote awareness of respiratory problems caused by ink fly and encourage members to report any symptoms. Keep health records.
|Contact with uncured UV ink
||Consider less irritant substitutes and enclosed handling systems. Use impervious aprons, gloves, etc., and eye protection|
|Inhalation of UV inks/ink fly
||Upper and lower respiratory tract irritation. Potential sensitization.
||Reformulation of inks, etc. Shrouding of rollers and local exhaust ventilation.
|Contact – wash-up solvents
||Skin irritation. Upper and lower respiratory tract irritation.
||Use local exhaust ventilation. Develop and implement safe work procedures, including use of PPE for circumstances such as spillage and leakage. See Hazards Watch on solvents.
|Inhalation of ozone
||Eye, nose, and throat irritation. Headaches and nausea.
||Local exhaust ventilation.
||Ocular irritation to varying degrees, which may temporarily cause difficulty with vision. Skin burns.
||Fixed or interlocked screening. Suitable goggles and skin protection during certain maintenance work.