Control Banding as a Risk Assessing Tool

Assessing risks in the lab and managing them can be complex due to the many diverse hazards and types. Exposure assessing is a challenge to do between the various equipment, needed expertise, time constraints, and analytical or labor costs. Also, exposure limits for many chemicals aren’t current with science or lack adequate evidence. What other options exist to effectively assess and manage risks? 

One method of systematizing is banding “like things” into similar groups. This can make it easier to understand, assess, and manage them. This can and should be done with hazards, exposures, and controls. All three are well-suited for approaches using banding and each can be sorted into similar groups. 

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What is hazard banding?

Hazard banding is grouping similar hazards for the purpose of recognizing and evaluating them. This often helps describe the hazard and assess its likely severity. We do this already with chemicals, biological agents, radiation sources, and physical hazards. We can also use routes of entry into the body, such as (inhalation, ingestion, skin absorption, or injection, to assess all three risk factors (i.e., severity, exposure, and probability). An example of severity is eye irritation vs. vision impact vs. total loss of sight.

Within chemical hygiene, there are more sub-groups. Six of these are ignitables (including flammables and combustibles), corrosives (acids and bases), reactives (air, water, other chemicals), oxidizers, toxins (all types), and asphyxiants (simple vs. chemical). 

Biosafety also has defined risk groups. Risk group 1 agents (e.g., chicken pox and e. coli) aren’t treated the same as risk group 2 (e.g., hepatitis, RSV, and Lyme disease). Nor are risk group 3 agents (e.g., West Nile, TB, and SARS) managed the same as risk group 4 (e.g., Ebola and Marburg). 

Radiation is well divided between ionizing and nonionizing. Further subtypes of ionizing include alpha, beta, gamma, neuron, and x-rays. With nonionizing, lasers are managed differently from UV light or microwave radiation. We can and should go further in our divisions and similar groupings. 

Flammability classes have varying degrees of risk. Toxins can be divided by target organs in a practical way. Corrosives too can be divided by types and concentrations. HF, nitric, and HCl all present different risk types and levels. 

How can it be done?

There are a few ways to perform control banding as a risk assessment tool. One way is to use target organs for toxicity to create hazard bands. “Target organ hazard bands” apply to chemical, biological, and radiation types of hazards. We don’t want people exposed nor any organ harm. That said, there are some significant risk differences between target organs. Teratogens targeting reproductive organs is an obvious dividing line for a lab with younger workers. Also, if one or more staff have lung or breathing problems then we should focus on pulmonary toxins as a band.

Exposures aren't always obvious and may be invisible to unaided eyes.

Ignitability has existing types and divisions. These include pyrophoric chemicals, flammable gases and vapors, combustible dusts, and ignitable fibers. As an example, flammability is primarily divided by its flash point—the temperature at which a vapor will ignite and propagate a flame. A class IA or IB flammable liquid, like gasoline, is much more hazardous than higher classes of flammables or combustibles, such as diesel fuel, due to gasoline’s much lower flash point of -45^oF (-43^oC). 

Corrosivity is obviously divided by acids versus bases. Further sorting is done by strength, but also acid types have some significant differences in risk (e.g., HF, nitric, and HCl). 

What is exposure banding and how can it help?

Exposures aren’t always obvious and may be invisible to unaided eyes. Collecting and analyzing samples is complex, time-consuming, and can be costly. Typically, banding is a semi-quantitative attempt to assess exposure. 

Exposures have three parts—a source, a path, and a receiver or worker. Exposure assessing and banding focuses on the source, then the path. The worker is assumed to be present. How much is aerosolized or vaporized can be a challenge to determine accurately, but amounts, concentrations, and degrees of a substance can often be approximated within a range. This can be described as low, medium, or high, for example. Often, we use the lab process and associated tasks as proxies for aerosolization concerns. Here’s a method to assess exposure bands by asking questions:

• Is it an open or closed process? Open will always release vapors 
• What’s the chemical vapor pressure? Higher VP means more will evaporate into the air
• How much surface area is there?  With more exposed such as a spill, more is in the air
• Is it being heated? That, too, drives up air concentrations 
• Does the reaction generate vapor? Is it captured or not? 
• If it’s a solid, are we dividing it into smaller particles easily aerosolized like grinding or mixing? 
• Is there potential for skin absorption or direct harm to the skin?

Each of these can be given a rating (number or letter) and placed on bands from low to high. As we address each question or factor, we add another rating to help calibrate our exposure bands. 

What is control banding?

Similar types of control measures or methods are easily used as control bands. These include ventilation for exposures, segregation for reactivity, and bonding, grounding, and ignition-suppression for flammables. Typically, we don’t have to start from scratch. Many exposure scenarios have previously been well addressed. So, we can use this limited set of vetted approaches as our banded methods of controlling hazards. 

How might it work? 

It’s best to use prevention-through-design and the hierarchy of hazard controls (figure 2) as guiding principles. Each level is a control band with the topmost ones being the most effective at reducing exposures and thus mitigating risk. As engineering controls for exposures, we tend to repeatedly reuse fume hoods, glove boxes, and biosafety cabinets (BSCs). For instance, an open process with a carcinogen like benzene will always be done in a fume hood. Pathogens similar to others in biosafety level 2 will also need to be performed in a BSC. Here are the steps (as questions) to work through the hierarchy of controls: 

• Can we eliminate the use of the hazardous substance?
• If not, is there a similar substance with a lesser hazard we can substitute?
• Can we isolate either the hazard or the worker from each other?
  • Is it a closed system? 
• What engineering controls can we use? 
  • It’s likely the most commonly used band
  • It includes fume hoods, biosafety cabinets, radiation shielding, guards 
• Any work practices to further reduce our exposures? 
  • Use wet methods to reduce aerosolization
• Any administrative controls to make a difference? 
  • Special training on high hazards like HF acid, prions, or Cesium are critical
• Which PPE is needed?
  • We often use goggles rather than safety glasses, plus a face shield for mucus membranes, and a rubber apron for strong acids 

Key takeaways

Banding of hazards, exposures, and controls are helpful approaches to further ensuring a safe lab environment for your staff. There are both qualitative and semi-quantitative aspects that aid the assessment process. Existing groupings and categories are established for some substances and can be used as a starting point. With a little thought, a lab can further use these tools to reduce exposures to hazards and thus manage their risks.