Exposure Assessment
3M Centre for Respiratory Protection
Respiratory Exposure Assessment
As a safety manager, you need to ensure you’re using the right respiratory protection measures and equipment. To do that, you’ll first need to know the types and levels of airborne contaminants in your job site. A thorough and well-documented exposure assessment process will help you:
- Identify potential health risks to workers.
- Prioritise those risks so you can tackle the most serious first.
- Measure exposure levels to see if they’re acceptable or not.
- Develop a plan to control unacceptable exposure levels.
- Keep records of exposure for communicating to workers and complying with government regulations.
One
Basic Characterisation
In this step, gather information about your workplace: information about the chemical and biological agents present, the workers and their assigned roles or tasks, and the controls you already have in place to ensure respiratory safety.
Start by collecting as much data as you can. The Safety Data Sheets provided by the manufacturers are a good source for answering many of the following questions, but you may have to dig deeper as well.
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Chemicals
- What specific chemicals (not trade or in-house names) are present?
- What physical form are the contaminants: gas, vapour, mist, particulate?
- What are the warning signs of exposure, like irritation or odour?
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Toxicity
- Could the chemicals have acute effects — short, immediate effects, usually with high-exposure situations?
- Could they have chronic effects from lower exposure, with symptoms that may not appear immediately?
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Sources and Routes of Exposure
- What are the tasks, routine and otherwise, that generate contaminants?
- Is inhalation one of the ways your workers could potentially be exposed to the hazard?
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Occupational Exposure Limits
- What are the acceptable exposure levels? Consult Worksafe New Zealand website (search under Workplace Exposure Standards and Biological Exposure Indices) and manufacturers’ suggested occupational exposure limits.
Two
Similar Exposure Groups
It’s not usually practical to measure every worker’s exposure, so you can assess your workforce by determining similar exposure groups (SEGs). If a group of employees perform similar tasks at the same frequency, using similar materials and methods, they can be considered an SEG. You only need to measure exposure for one of each group.
SEGs can be grouped by:
- Task and contaminant
- Task, process and contaminant
- Task, process, job classification and contaminant
- Work teams
If you have past exposure monitoring data, it can help you determine SEGs, too.
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Workforce
How is your workforce organised? List tasks, who’s assigned to them, how your staff is organised (by team, department, etc.), and the number of people assigned to each task or group.
Three
Qualitative Assessment and Prioritisation
Once you’ve gathered data on workers or SEGs, each person or group’s potential exposure should be ranked. This will help prioritise the most serious risks so you can monitor them first.
Prioritisation should be based on two measurements:
1. Workers’ or SEGs’ potential for exposure to each chemical present in the workplace. Rank from 1 to 4, with 1 meaning typical exposure is expected to be less than 10% of the exposure limit for that agent, and 4 meaning typical exposure is expected to be greater than the exposure limit. You can base your determination on:
- Past monitoring results at your workplace.
- Published data about similar situations.
- Exposure modeling using mathematical models.
2. The health effects of overexposure to the contaminant. Using the toxicity data gathered during basic characterisation, rank health effects from 1 to 4, with 1 meaning minimal adverse health effects and 4 meaning life-threatening or disabling.
Four
Exposure Monitoring
Monitoring enables you to identify any unacceptable exposures. There are three reasons for exposure monitoring:
- Baseline — to determine the current level and range of exposures.
- Diagnostic — to identify specific sources of the contaminants so you can develop control methods, such as making engineering changes or providing respirators.
- Compliance — to meet regulatory requirements for a specific agent that has more stringent rules, such as asbestos or lead.
How many samples to take depends on your objective. Professional judgment should be used in all cases, plus:
- For baseline monitoring, you could rely on statistical methods (typically 3 to 10 random samples).
- For compliance monitoring, following Worksafe New Zealand guidelines/regulations for that contaminant.
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Personal Monitoring
Personal monitoring is when samples are collected by attaching a monitor directly to the worker. How long you need to monitor to collect each sample depends on the chemical’s occupational exposure limit and what you’re trying to achieve. For example, you could take:
- Full shift or 8-hour time-weighted average (TWA) samples.
- Task-based samples — taking samples for the duration of a specific task (like grinding concrete).
- 15-minute short-term exposure limits (STEL) or ceiling samples to determine peak exposure levels.
Certain airborne substances can be collected on-site and analysed by certain laboratories, or in some cases with direct reading instruments. In most cases, the contaminant must be identified in advance, so you can use the appropriate monitoring equipment and procedures.
For information on 3M monitors and recommended laboratories, please contact your local 3M representative.
Five
Interpretation and Decision-Making
The criteria for evaluating exposure assessment results should be determined by a safety/health professional prior to exposure monitoring. Once you collect all the necessary data, it must be evaluated to determine whether the exposures are acceptable or not:
- Acceptable exposures indicate you may not need to take any action.
- For unacceptable exposures, you’ll need to decide what action is required to manage the exposure, such as installing engineering controls and/or introducing respiratory protection equipment.
- If there’s insufficient data to make a decision, you’ll need to conduct more assessments and re-evaluate.
Six
Reporting
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Each time you conduct an exposure assessment, make sure there are detailed records of it, including:
- A summary of what was done.
- The purpose of the monitoring.
- Basic characterisation results: task or work group and process descriptions.
- Explanation of SEG groupings.
- Exposure criteria selected — TWA or STEL — and why.
- Results tables of qualitative assessment and prioritisation.
- Health effects of over exposure to the contaminants, including copies of safety data sheets.
- Monitoring and analytical method used.
- The conclusions drawn from the data — whether levels are acceptable or not.
Recommended changes:
- Changes to try to control the exposure
- Respiratory protection equipment
- Future assessment schedule
- Any other references used during the process.
Like all parts of your respiratory safety program, exposure assessment is an ongoing responsibility. Even when exposure levels are acceptable, you’ll need to re-evaluate periodically and anytime a new procedure, chemical or workplace change is introduced.
Finding Outside Help
Recommendations
If you don’t have trained safety professionals on staff, you’ll need to hire an outside consultant to conduct your assessment. Even if you have trained professionals, you may want to bring someone in. A consultant may be able to handle the entire process for you or just the parts you need help with.
You can hire an independent outside consultant, or bring in a loss control representative of your workers compensation carrier. Federal and state occupational safety and health departments or local universities sometimes offer consulting programs, too.
The New Zealand Occupational Hygiene Society (NZOHS) website can help you locate an independent consultant.
See the next step in your journey to optimising your respiratory protection program.
