OR WAIT null SECS
Patricia Atkins is a Senior Applications Scientist with SPEX CertiPrep and a member of both the AOAC and ASTM committees for cannabis.
An in depth look at the most common PPE in laboratories and cleaning procedures that can be enhanced to increase safety.
During times of the COVID-19 pandemic, many laboratories are continuing to operate. Cannabis laboratories which are still operating face the same issues of safety and protection as the rest of the world’s laboratories. In this column’s edition, we will take an in depth look at the most common personal protective equipment in laboratories as well as cleaning procedures that can be enhanced to increase the safety of the laboratory personnel.
Most laboratory personnel are familiar with common laboratory personal protective equipment (PPE), but there are some differences in equipment and use that one often takes for granted as correct. There are different uses for each type of PPE and different ratings for equipment such as masks, respirators, gloves, and so forth that are dependent on the function they are intended for in the laboratory. There are some specialized PPEs that are only used in specific settings, which tend to benefit the laboratory’s clean setting rather than the laboratory technician.
Safety glasses, googles, and face shields protect the eyes of the wearer from a variety of substances, projectiles, biological agents, and other ocular dangers. Every day, about 2000 workers sustain eye injuries on the job and more than half are because of improper or lack of eye protection (1). Eye safety standards are dictated by several organizations including Occupational Safety and Health Administration (OSHA) and American National Standards Institute (ANSI).
Safety glasses are one of the most common eye protectors in the laboratory. These glasses should fit properly and have side shields in laboratories where projectiles or splashing is possible. OSHA requires safety glasses provide protection from hazards for which they are designed and can be disinfected. There are different classes of safety glasses and goggles with different ratings depending on their purpose and level of protection. All safety eyewear must withstand various impact tests and are rated as either high impact or basic impact.
Basic impact ratings are determined by a “drop ball” test where a 1-in. diameter steel ball is dropped from 50 ft. onto the lens. High impact ratings are performed by shooting a ¼-in. steel ball at the lens at a speed of 150 ft/s. These high impact glasses have a “+” marking imprinted with the manufacturer’s trademark on the glasses; where basic impact glasses lack the “+” marking. ANSI ratings designate “+” as impact rated glasses and the unmarked variety as nonimpact rated (Table I).
Safety glasses can have a variety of different colored lenses, shading, and coatings appropriate to their application. Shaded lenses can help protect eyesight from bright light exposure from activities such as soldering, welding, and ampule sealing. The primary composition of safety glasses are plastics, such as polycarbonate.
Safety glasses only protect the wearer from flying particles and small debris or splashing. In laboratories where there are possible exposures to chemical fumes, gases, vapors, large splashes, or biological hazards, more protection is needed in the form of goggles, face shields, or full face respirators. Goggles are the next level of eye protection in the laboratory. They provide more protection from chemical and physical exposure than laboratory safety glasses. There are three basic types of goggles: direct vented goggles, indirect vented goggles, and nonvented goggles (Figure 1).
The first type of goggles (direct vented) allows free flow of air through the goggles with openings in the vented areas that are smaller than 1.5 mm. This type of goggle does not fully protect against vapors, biologicals, or splashes in the laboratory.
Indirect goggles have covered vents so there is no direct straight passage of air or hazards from the outside of the goggle to the inside. This type of configuration limits exposure from liquid splashes, but not from fumes, gases, or airborne biological agents.
The final type of goggles is nonvented goggles that have no passage or vent through the goggle in which the wearer can be exposed to vapors, chemicals, and biological agents. These types of goggles may or may not be gas-proof depending on material and rating. The primary component materials for goggles are combinations of polymers such as polycarbonate, polyvinyl chloride, and so on.
Another type of eye and face protection is a face shield. Face shields have become a point of discussion and debate during the COVID-19 pandemic. A face shield is a physical barrier to protect people from hazards such as projectiles, molten metals, and many forms of chemicals and chemical reactions. Face shields are intended for use in conjunction with glasses or goggles. Face shields do not offer protection from airborne biological contaminants, airborne mists, vapors, or gases. The Centers for Disease Control and Prevention (CDC) does not recommend the use of face shields as a replacement for masks.
As in the case of safety glasses and goggles, most face shields are made from plastics. The material selected for the face shield and other face and eye protection equipment must be examined for its chemical and physical characteristics to determine if it is suitable for different laboratory uses. Protective face and eyewear also must be properly fitted to provide optimal protection.
Respirator face masks and face shields cover different parts of the face but generally cover the mouth and nose. Face shields offer the least amount of respiratory protection since they are only physical barriers to splashes and respiratory expulsions directed at the face. Face masks offer some level of respiratory protection depending on the material, type, and specifications of the mask.
In the current pandemic, many types of face masks have become commonplace to protect against respiratory spread of the virus, but recent studies by Fischer and colleagues have shown significant differences on disease transmission based on the material and type of face mask (3). The most efficient masks were fitted N95 masks (trap up to 95% of particles) and surgical masks in relative droplet count. The highest droplet counts were found when either not wearing a mask or wearing a bandana or neck gaiter type of face covering. Face masks can be a tool for the filtration of particles depending on their rating. Fitted face masks are very different from the surgical masks and cloth masks being seen in pictures during this outbreak. All of the world organizations warn that a generic face mask is not a substitute for a fitted and regulated face mask or respirator. The question comes up regarding the differences between these masks and respirators. The answer is the level of protection and intended use.
Cloth masks have been recommended by the CDC to prevent the spread of COVID-19 to others (4). Cloth masks and coverings are the most basic form of mask and are not considered to be personal protective equipment. These masks do not make a close seal to the face, are not fitted, and primarily are meant to protect others from the wearer of the covering.
Surgical masks or medical masks are loose-fitting coverings for the mouth and nose. These types of masks are intended for medical workers and are often fluid resistant to prevent some fluid transmission coming to and from the wearer. Most surgical masks are not considered to be a form of respiratory protection by the CDC. Masks that are tested under ASTM standards can be classified by filtration efficiency, fluid resistance, differential pressure, and flammability. Level 1 masks offer the lowest amount of protection and level three masks offer the most protection (5) (Table II).
Fluid resistance measures the resistance of the mask to penetration by liquids at high velocities with level three masks having the most protection. Differential pressure or breathability determines airflow through the mask with level one having the most airflow but the least protection. Bacterial and particle filtration relate the percent filtration of bacteria and particles above designated sizes. The flame spread or flammability exposes masks to a flame and measures time of spread. Class one materials means normal flammability and can be used as clothing.
Cloth masks, in general, do not provide the wearer with the highest level of protection but do help contain respiratory droplets. These masks are not true forms of PPE like respirators or other methods of face protection. Surgical or medical masks can offer some protection depending on their type and fit. The more efficient face protections are the fitted masks and respirators.
Respirators filter particles, chemicals, and fumes depending on their specification using filtration chemicals or materials (Table III). Respirators are meant to protect the wearer from these agents and must be properly fitted and tested by a professional to ensure good seal and appropriateness for use. Respirators can either be designated as single use or as reusable depending upon material and filtration.
In the chemical laboratory, the most commonly used respirators are either air-purifying respirators for particles, gases, or a combination of laboratory hazards. These respirators can have different levels of coverage from full face to filtering facepiece respirators (FFRs) and are rated by OSHA for an Assigned Protection Factor (APF). The APF of a facepiece gives the user the reduction of exposure expected with proper use and fit. An APF of 10 means the user’s exposure is reduced by 10% or 1/10th the exposure with proper use (6) (Figure 2).
Full facepiece respirators are a reusable respirator that employs cartridges, canisters, or filters and cover the entire face. The facepiece is made from a moldable material such as silicone or rubber that creates a seal with the face and must be fitted within a safety testing program. The full facepiece has a full clear plastic lens for eye protection. This respirator covers the face from the hairline to under the chin. The APF for a properly fitted full facepiece is about 50.
A half facepiece respirator is similar to full facepiece respirators but lack the eye protection. These respirators lack the clear lens to protect the eyes and stop at covering the nose and mouth. These respirators can have the same types of filters and canisters found in full facepieces and the APF for most of these types of fitted devices is 10.
Filtering facepiece respirators (FFRs) remove particles from the inhaled airstream or path of the wearer and can include what we commonly refer to as N95 masks. OSHA defines FFR as a negative pressure particulate respirator that has an integrated filter as all or part of the facepiece (7). The letter designation of masks or respirators refers to whether the item is non-resistant (N), somewhat resistant (R ), or strongly resistant to oil (P). The number component determines the amount of particles filtered by the apparatus. An N95 respirator mask is not resistant to oil and filters at least 95% of the airborne particles. A P100 mask is strongly oil resistant and filters almost 100% (99.97%) of particles. FFRs form a seal around the user’s face and cover the mouth and nose, some are equipped with values. Often, N95 and other FFRs are disposable but there are some forms that can be cleaned and reused according to the manufacturer’s directions.
All respirators for proper use and protection must be fitted and undergo some form of fit testing to prove there is an air-tight seal before the masks or respirators are used. Most fit testing is completed prior to the first use of the mask, or when there is a change in type or model of respirator, a physical change to the person wearing the device, or on an annual basis.
Fit testing can be qualitative or quantitative. Qualitative fit testing relies on the senses of the wearer to subjectively report taste, scent, and irritation to four test agents: banana oil, saccharin solution, a bitter solution, and irritant smoke (8). A quantitative fit test uses the same solutions but asses fit to a numerical response to measure penetration into the respirator. For more information, refer to CDC, OSHA, National Institute for Occupational Safety and Health (NIOSH), and International Organization for Standardization (ISO) guidelines and instructions on selection and use of respirators and masks.
While respirators can be important tools for some laboratories and face masks are now part of daily life, it is more common that chemists and other laboratory scientists use basic PPE such as gloves and lab coats in addition to the goggles and safety glasses. All of these PPE items are needed for chemical protection but can also be used for protection against biological agents. As with face protection, there are different classes of body coverings that are dependent upon use.
Gloves as well can be made from a variety of materials which is important to understand since each type of glove has its own strengths and weaknesses. Many gloves are subject to issues of chemical or biological resistance, meaning not all materials are resistant to all agents and therefore offer limited protection. The factors in selecting disposable laboratory gloves are permeation, degradation, and size.
Often laboratory employees don’t consider the size of a glove to be a factor in their effectiveness or the ability to work. Gloves that are too small can cause the material to be stretched too thin and become more permeable and subject to punctures. Small gloves can attribute to hand fatigue and irritation from pressure or rub points. Gloves that are too large can hinder movement and dexterity, which can cause accidents. Large gloves can slip off during use and if there is a rip or tear it may not be noticed because of the extra glove material.
Gloves should be measured using the dominant hand by wrapping a tape measure to encircle the width of the hand or using a measurement from the wrist to the top of the middle finger. The measurement can then be converted into standard glove sizes or lettered glove sizes depending on the manufacturer (9). Medium gloves are meant for approximately a hand width of 8–9-in. with the subsequent sizes measuring up or down in about 1-in. increments. Medium gloves can accommodate a length of about 7 3/16-in. Please consult your glove manufacturer for proper fitting.
In addition to glove size, the chemical compatibility of laboratory gloves needs to be examined to ensure proper protection. Some gloves and other protective clothing, tested by ASTM or ANSI methods can be given a rating for chemical degradation and permeation. Degradation testing measures the effect of a chemical on the glove material as a percent weight change of the material. A percentage change of more than 30–40% in most cases is considered to be poor or not recommended for use with that chemical (10). Permeation resistance testing measures the rate chemicals can pass through the glove material in units of time to breakthrough or permeation rate (11) (Table IV).
In a tragically famous case of chemical exposure through gloves, a professor at Dartmouth College, Karen Wetterhahn, was preparing a dimethylmercury standard in a fume hood when one or two drops of the solution inadvertently spilled onto her latex gloves. She was working in a fume hood and wearing PPE, so she finished her preparation then removed the gloves and washed her hands. Several months later she was diagnosed with dimethylmercury poisoning. It is believed that the mercury solution permeated her latex gloves in less than 15 s. In less than a year after her exposure, Professor Wetterhahn died from her exposure.
Most disposable gloves common to chemical laboratories have lower resistance, higher permeation rates, and are faster to degrade than reusable gloves. Disposable gloves are only meant for incidental contact rather than prolonged exposure. These types of gloves should be disposed of immediately upon contact with a chemical or agent and replaced with new gloves after washing the hands. Intentional or prolonged contact with chemicals requires sturdier gloves made of durable materials with sufficient thickness to stop or delay permeation and degradation.
The safety data sheets accompanying chemicals contain all the information regarding the safety and compatibility of those chemicals. The health and safety sections will often list conditions of use and safety precautions such as PPE required, glove materials suggested along with thickness of gloves and other materials. These data sheets also carry information on safe handling and disposal, which should be followed when disposing of PPE that may have been contaminated with that material.
The choice of the proper PPE is not the only factor in protection for the wearer. The matter in which PPE is put on and removed after use is important. Gloves, as was stated previously, should be of a compatible material for the purpose and must fit snugly but not so tight that they stretch and become compromised more quickly during use. Gloves should also not gap at the fingers.
After gloves are contaminated they can be removed by pulling one glove off with the still gloved hand and then using the inside portion of the glove to remove the second glove folding them into each other so the glove disposal packet has the contaminated or exposed areas contained inside
Laboratory coats should fit properly and button. The cuffs should not hang down into the work area nor should the cuffs be too short to not cover the tops of the gloves when worn. Pockets should not contain items that cannot be exposed to contamination or infection. Laboratory coats should be changed frequently. The removal of the laboratory coat is similar to the gloves where the sleeves are removed inside out and the outside is folded inside to contain the contaminated area. The material of the laboratory coat or aprons should have the same chemical compatibility and resistance factors as other PPE in use.
Many PPE items in the laboratory are disposable such as some gloves, face shields, and masks. Other items such as respirators, glasses, reusable gloves, and laboratory coats will need maintenance and cleaning. The first step in any cleaning is to check the manufacturers packaging, literature, and website for cleaning and compatibility instructions.
Many cleaning procedures detail some application of a cleaning product that will remove debris and contamination, but not damage the materials of the PPE. For example, if a respirator is being cleaned with an aggressive solvent such as acetone, it might melt or deform the plastic material and make the PPE unfit for use.
Cloth items such as aprons and laboratory coats should only be cleaned by professionals using the correct handling procedures. Laboratory coats and other labware should never be placed in home or residential washers and dryers where they could cause more contamination, infection, or damage to people and equipment. Laboratory coats should be cleaned before significant stains and spills are visible.
The first step to safety in a laboratory is cleaning and organization. To disinfect a laboratory properly against biological contamination it first must be generally clean. Dust and dirt attract and collect particles and chemicals. A thorough cleaning procedure must account for all areas from the ceiling to the floor to remove dirt and debris. Filters must be changed in hoods and environmental control systems. Trash must be removed and clutter discarded. After general cleaning, the process of disinfection can then occur. There are many chemical agents that can be used to disinfect a laboratory for viruses.
There are many commercial products for all types of settings. Most of these products have familiar active chemical agents such as alcohols, acids, chlorides, and so forth. The mode of action for these products is usually one of the three processes: dehydration of the biological agent or inactivation of chemical agent, disruption of cellular structures or chemical processes, or denaturing proteins and genetic materials.
The Environmental Protection Agency (EPA) has published an extensive list of all of the commercial products for use in cleaning against viruses and COVID-19 on their website (13) (Table V). Commonly used laboratory solvents call be used for cleaning and disinfection including: ethanol, sodium hypochlorite, and more (Table VI) (14,15).
The common theme for all of these products, whether they are commercial products or laboratory produced disinfectants, is dwell time or contact time. Dwell time is the amount of time needed for the active agent to be in contact with a surface to be effective. There are very few instantaneously effective products and in most cases the solution needs to be applied for up to 10 min before wiping or washing the surface clean to ensure proper disinfection.
It is important to remember in the use of cleaners and cleaning agents that they are still chemicals capable of contaminating daily processes and operations. Alcohols and other solvents are common laboratory materials and may contaminate sensitive areas that may be used to measure volatile organics. These compounds can also kill microbiological experiments if not properly vented from the laboratory workspace. Chlorine compounds and acids can cause oxidation and contaminate experiments, metal components of instruments and equipment. Additional actions may be needed to ensure normal laboratory processes are not contaminated by the updated cleaning procedures.
Before cleaning and disinfecting an area, all porous materials such as paper, paper towels, and so on should be removed from the areas to be cleaned so as not to absorb chemicals. Select cleaning agents appropriate for the area to be cleaned with thought in mind as to the type of work that occurs in these areas and how that work will be affected by these agents. If possible, airflow and hood flow should be increased to drive fumes away from work areas. Chemical odor traps can be used to absorb volatile chemical fumes. Hoods and sensitive areas should be decommissioned during cleaning and allow several hours for fumes to dissipate.
Multiple spot cleanings should be scheduled during a shift with a plan for more extensive cleaning on a periodic basis. Deep cleaning plans and services should be outlined in a cleaning plan upon an exposure within the laboratory. Personal cleaning and hygiene plans as well as expectations should be discussed or notices posted to remind everyone to keep a cleaning plan in use.
Common laboratory procedures and practices are designed keep scientists safe from chemical and biological exposures. Now, at this time of heightened awareness it is appropriate to examine those practices and the personal protective equipment used in our laboratories to ensure that the tools meet the tasks. The everyday gloves we use in the laboratory are not one type or one size fits all purposes. Read the documentation for the PPE you are using and determine if it will protect you not only from the threat of biological exposure, but from the everyday solvents and acids that are part of your workflow. During this health crisis, use the opportunity to educate and improve upon the safety and cleanliness in the laboratory.
PATRICIA ATKINS is a Senior Applications Scientist with SPEX CertiPrep and a member of both the AOAC and ASTM committees for cannabis.
P. Atkins, Cannabis Science and Technology 3(8), 18-26 (2020).