The National Institute for Occupational Safety and Health (NIOSH) functions as an agency under the Centers for Disease Control and Prevention (CDC) responsible for conducting research and making recommendations to prevent work-related injury and illness. The NIOSH health-hazard evaluation (HHE) program is available for employees, employers, or union representatives to use for an investigation of health and safety concerns.
The National Institute for Occupational Safety and Health (NIOSH) functions as an agency under the Centers for Disease Control and Prevention (CDC) responsible for conducting research and making recommendations to prevent work-related injury and illness. The NIOSH health-hazard evaluation (HHE) program is available for employees, employers, or union representatives to use for an investigation of health and safety concerns. This may result in sending the requestor information, referring them to a more appropriate agency, or making a site visit, which may include environmental sampling and medical testing. After a site visit, we prepare a report that includes recommendations to correct problems.
This article discusses an HHE we conducted at a small screen-printing company to address potential occupational exposure hazards. It includes our findings and recommendations provided in the ensuing report.
We received an HHE request from a company that designs and screen prints acrylic signs for a variety of businesses. Housed in a four-story, 35,000-sq-ft building, the company employs 22 people with only three involved directly in screen printing or spray painting. Company management and employees were concerned about possible harmful health effects from exposures to organic solvents in lacquer thinner and screen-printing inks.
We visited the facility to collect air samples, measure airflow in the spray-paint booth, check air movement in the screen-printing area, evaluate personal protective equipment (PPE) use, and identify fire safety hazards. Workers were mostly exposed to breathing solvent vapors during screen printing and washing. However, they were also exposed to vapors from evaporation of solvent-soaked cleaning towels. Additionally, workers had skin exposure to solvents.
We took air samples for toluene, n-hexane, isopropyl alcohol, acetone, and cyclohexanone. Air-monitoring results indicated that full-shift exposure to these individual chemicals did not exceed occupational exposure limits (OELs) established by the Occupational Safety and Health Administration (OSHA). However, exposure to the mixture of solvents was slightly above the American Conference of Governmental Industrial Hygienists (ACGIH) recommendations. Short-term exposure to isopropyl alcohol during screen printing and screen washing could exceed short-term exposure limits (STELs).Advertisement
We recommended that the company consider using non-solvent or low-solvent alternatives for screen printing. The screen-printing area did not have exhaust ventilation, and there was little air movement in the work area. During warm weather, a window near the screen-printing table is opened and a fan used to blow air out. However, opening the window and using a fan might not improve ventilation enough. Therefore, we recommended installing an exhaust ventilation system for screen printing.
We observed work activities that might cause splashing of screen-printing chemicals into the workers’ eyes or hands. Although workers wore latex gloves when cleaning screens, they did not wear gloves during other screen-printing activities. Additionally, the latex gloves that were available were not appropriate to protect against the chemicals in lacquer thinner and screen-printing inks. Based on the primary ingredients in these types of products, we recommended gloves made of Viton/butyl combination or laminate plastic film such as Ansell Barrier (polyethylene, polyamide, polyethylene combination) or North Silvershield/4H (polyethylene, ethylene vinyl alcohol, polyethylene combination). Workers also did not wear any eye protection. Therefore, we recommended that they use safety glasses or goggles when handling hazardous chemicals (Figure 1).
We identified several fire safety hazards at the facility. Employees stored lacquer thinner in plastic containers that were not approved for flammable liquids. We recommended that the company provide proper flammable safety containers (Figure 2). Too much lacquer thinner was stored in the spray-paint booth, so we advised the company not to permit more than a one-day supply of lacquer thinner or screen inks to be stored there. We also found that containers were not properly bonded when flammable liquids were poured from one container to another. To prevent possible accumulation of a static charge and spark, we recommended the company require the use of bonding cables to electrically connect containers of flammable liquids when pouring from one container to another. Lastly, we recommended that flammable liquids be stored in the flammable-material-storage cabinets.
To eliminate or minimize workplace hazards, we encourage (in order of preference) the following controls: substitution or elimination of the hazardous agent, engineering controls (for example, local exhaust ventilation, enclosure, dilution ventilation), administrative controls (for example, limiting exposure time, training, work-practice changes, medical surveillance), and personal protective equipment (for example, respiratory protection, gloves, eye protection). In most cases, the best approach is to eliminate hazardous materials and install engineering controls to reduce exposures. Until such controls are in place, or if they are not effective, administrative measures and/or personal protective equipment may be needed.
Inhalation of solvent vapors
Organic solvents may cause minimal to mild irritation of the respiratory system. Irritation usually affects the upper airways, mucous membranes, and eyes, and it generally ends quickly without long-term effects. Solvents can also cause neurologic problems such as fatigue, poor memory, irritability, difficulty concentrating, and mood changes. It is not clear how many of these problems will last after exposure has ended. Symptoms of significant solvent exposure are similar to being drunk (headache, nausea, vomiting, dizziness, slurred speech, impaired balance, poor concentration, disorientation, and confusion). These symptoms go away quickly after exposure has ended. Death from breathing difficulties can occur at very high levels, but this is very rare.
Skin exposure is a major route of exposure to organic solvents. Solvents dissolve the protective outer layer of fat in the skin and allow chemicals to be absorbed into the body. Almost all organic solvents cause skin irritation because they remove fat from the skin. Skin disease is the second most common type of occupational disease. NIOSH has a Website on skin exposure, www.cdc.gov/niosh/topics/skin.
Eyes may be exposed to organic solvents or other hazardous chemicals by splashing or by contact with vapors. This can cause chemical burns or damage to eyes. NIOSH has an online topic page that discusses eye safety, www.cdc.gov/niosh/topics/eye.
The screen-printing process may involve lacquer thinners or inks, which are flammable. Flammable liquids must be used and stored properly to prevent the build-up of flammable vapors that can ignite easily and start a fire. In addition, sources of ignition, such as pilot lights, static electricity, open flames, sparks from electrical circuits, or welding, must be kept away from flammable vapors (see the section about fire safety below for a link to the National Fire Protection Association’s online guidance on safe storage, handling, and use of volatile substances).
General recommendations for screen-printing companies
So, how can screen printers and management reduce or remove potential hazards? Consider the following actions, in order of preference:
Elimination and substitution Investigate whether non-solvent or low-solvent inks and screen washes can be used. Contact trade organizations, such as the Specialty Graphic Imaging Association (www.sgia.org), to determine which non-solvent or low-solvent inks or screen washes are available and whether other companies use them successfully. Eliminating or substituting a hazardous chemical is effective because it reduces the need for additional controls.
Engineering controls Improve ventilation in screen-printing areas. Effective ventilation can reduce employees’ exposure to air contaminants substantially. If you have poor ventilation, consult a ventilation engineer to make necessary improvements for your specific environment.
Administrative controls Complete a PPE hazard assessment to determine whether hazards are present that require the use of PPE (safety glasses, protective gloves, respirators). Employees must be trained how to use and maintain their PPE. OSHA requires written documentation that the PPE hazard assessment and employee training have been completed. Information can be found on the OSHA Website (www.osha.gov/SLTC/personalprotectiveequipment/index.html).Advertisement
Implement a hazard-communication program. Such a program includes requirements for MSDSs, container labeling, training, and a written program. Information can be found on the OSHA Website (www.osha.gov/recordkeeping/new-osha300form1-1-04.pdf).
Require employees to follow standard operating procedures to reduce evaporation of solvents into the workplace. For example, this would include requiring preparation of materials immediately prior to use and proper disposal or containment of solvent-soaked materials.
Personal protective equipment (PPE)
Provide employees with respirators for use during screen-printing or spray-painting tasks when air-contaminant levels are above OELS. PPE is the least effective way to control employee exposures because it requires a high level of employee commitment and can result in adverse physiological effects. Use of respirators should not be the only method for limiting exposures, but should be worn until hazardous chemicals can be substituted or engineering (ventilation) and administrative controls lower exposures to an acceptable level.
Employees wearing respirators must be properly fitted, trained, and undergo medical evaluations. The company must prepare a written respirator program that documents how they comply with OSHA respirator-program requirements. Refer to the OSHA respiratory protection standard (29 CFR 1910.134) for information on proper use, maintenance, and storage, or to Appendix D of the standard if use is voluntary.
Provide chemical-resistant gloves specific to the type of chemicals in the lacquer thinner or screen-printing ink. To prevent skin exposures from chemicals, follow a reference guide such as Quick Selection Guide to Chemical Protective Clothing (see resources and links) to determine appropriate gloves, as well as other PPE, to use. Latex is not an appropriate glove material for screen printing because the solvents in inks or lacquer thinner can damage it relatively quickly, and some people are allergic to latex.
Provide and require employees to wear the appropriate protective eyewear when using hazardous chemicals and performing activities that might result in chemical splashes. The type of personal protective eyewear used must be chosen depending on the specific work situation and hazards and each person’s individual requirements.
Install an eye-wash station in the screen-printing or spray-painting area. The eye-wash station should be capable of providing adequate liquid for at least 15 minutes of drenching or flushing of the eyes. It can be either plumbed or self-contained. Refer to the OSHA standard in 29 CFR 1910.151(c) for more information about eye-wash stations.
Do not use plastic containers for any flammable or combustible liquids, such as lacquer thinner, unless the container has been approved by Underwriters Laboratory Inc. One example of a container for daily use of flammable liquids is an Underwriters Laboratory, Inc.-approved metal safety container with a plunger dispensing mechanism.
Electrically ground containers of flammable liquids, and make sure that dispensing and receiving containers are properly bonded before transferring flammable liquids.
Consider the quantity of flammable material being stored in the work area, and use flammable-material-storage cabinets. The National Fire Protection Association Standard 30: Flammable and Combustible Liquids Code has additional guidance on safe storage, handling, and use of volatile substances and is available at www.nfpa.org.
Lilia Chen and Scott Brueck are NIOSH employees; Maureen Niemeier is a contract employee of NIOSH working as a freelance technical writer.
Resources and Links to More Expanded Information
NIOSH HHE reports: www.cdc.gov/niosh/hhe
Forsberg K, Mansdorf SZ . Quick selection guide to chemical protective clothing. 5th ed. Hoboken, NJ: John Wiley & Sons, Inc.
NIOSH topic page on skin exposures and effects: www.cdc.gov/niosh/topics/skin
OSHA . OSHA Small Entity Compliance Guide for the Revised Respiratory Protection Standard. www.osha.gov/Publications/secgrev-current.pdf
NIOSH topic page on eye safety: www.cdc.gov/niosh/topics/eye
OSHA Respiratory Protection Standard and Information for Employees Using Respirators when not Required Under Standard – 1910.134 Appendix D.
OSHA guidance on PPE:
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