Workplace exposure monitoring

Last updated

Workplace exposure monitoring is the monitoring of substances in a workplace that are chemical or biological hazards. It is performed in the context of workplace exposure assessment and risk assessment. Exposure monitoring analyzes hazardous substances in the air or on surfaces of a workplace, and is complementary to biomonitoring, which instead analyzes toxicants or their effects within workers.

Contents

A wide array of methods and instrumentation are used in workplace exposure monitoring. Direct-read instruments give immediate data, and include colorimetric indicators such as gas detector tubes, and electronic devices such as gas monitors and aerosol particle counters. In addition, samples may be collected and sent to a laboratory for slower but often more thorough analysis.

Overview

Instruments typically used for monitoring of particulates: a condensation particle counter (left), aerosol photometer (blue device at top), which are both electronic direct-read instruments; and two air-sampling pumps for filter-based analysis Airborne nanomaterials detection equipment.png
Instruments typically used for monitoring of particulates: a condensation particle counter (left), aerosol photometer (blue device at top), which are both electronic direct-read instruments; and two air-sampling pumps for filter-based analysis

Exposure monitoring may be done for reasons of regulatory compliance, selection of hazard controls to implement, verification of engineering controls, reducing workers' compensation costs, or belief in a right or responsibility to understand health risks in the workplace. [1] : 41, 46 

Instrumentation includes direct-reading instruments, sampling pumps, and stationary monitoring devices. Samples need to be sent to a laboratory for analysis, which requires a delay of hours or days. By contrast, direct-read instruments provide data immediately. [1] : 8–9, 49  Direct-read instruments are sometimes used for screening before taking samples. [2] Calibration and maintenance is an important function, especially if quality assurance standards are mandated for that workplace. [1] : 8–9 

A monitoring plan requires understanding of the work tasks being performed and by whom, and the hazards associated with them. It is important to monitor a statistically representative population. Workers are often divided into "similar exposure groups" with similar work assignments and contaminant exposure profiles. Data must be validated, reported, and communicated. Exposure monitoring may be targeted to individual workers, or areas. [1] : 21, 46–47, 58 

Chemical warfare agents have extremely low occupational exposure limits that are below the sensitivity threshold for most typical monitoring methods, and often require specialized equipment. For biological agents, some methods can determine if a suspect material is of biological origin without identifying it, while identification requires other methods. [3]

Direct-read instruments

Colorimetric

A colorimetric gas detector tube in use Colorimetric gas detector tube.png
A colorimetric gas detector tube in use

Colorimetric testing devices contain substances that change color upon exposure to a certain substance. [3]

Gas detector tubes are glass tubes filled with a solid granular material incorporating a chemical color change reagent. Detector tubes are available for over 300 gases, vapors, and aerosols in air, with each tube specific for one or a few chemicals. Air may be passed through the tube with a hand pump or powered air pump for spot measurements, or by diffusion for long-term measurements. The chemical concentration is generally determined by the length of the color stain in the tube, although a few use a comparison of the intensity of the stain to a color chart. They are sensitive in the percent to parts-per-billion range. [4] The color change reactions include production of molecular iodine, precipitation reactions of metal salts, various addition reactions of aromatic compounds, redox reactions, and pH indicators. Other chemical reactions may occur before the color change reaction. [5] While fast and inexpensive, they generally only have accuracy within 20%, have the potential for interference with other chemicals, and may be temperature sensitive. [1] : 58–59 

For chemical warfare agents, specialized detection papers or kits, and colorimetric tubes can be used. For biological agents, protein paper and pH paper can indicate the presence of biological material, while identification can be done with handheld immunoassays and semi-portable polymerase chain reaction systems. [3]

Electronic

A multi-gas monitor with an instruction card Detector for Gas.jpg
A multi-gas monitor with an instruction card

Electronic direct-read instruments for gases include photoionization detectors, infrared analyzers, and gas monitors. For dust and particulates, instruments include aerosol photometers and condensation particle counters. [3] Handheld electronic monitors give instantaneous readouts, but can experience interference from similar compounds, and the user must be knowledgeable enough to calibrate the device, and interpret its results with the specific device's limitations in mind. Fixed air monitors do not require an operator and can be left on continuously. Electronic instruments may be designed to detect one or several gasses. [1] : 61 

Gas monitors may be single, dual, or multi-gas monitors. Some types include oxygen sensors, explosibility sensors for combustible gas, and toxic gas sensors for substances including carbon monoxide, hydrogen sulfide, nitrogen dioxide, sulfur dioxide, chlorine, chlorine dioxide, phosphine, ammonia, hydrogen cyanide, and hydrogen. Mercury vapor analyzers are also used. [3] Electrochemical gas sensors use a porous membrane (normally PTFE) or capillary system which allows the gas to diffuse into the cell containing the liquid or gel electrolyte and the electrodes, causing a change in electrochemical potential between the electrodes. Because of the low power requirements and small size, they can be used in personal monitors that have dosimeter and alarm functions. [6]

Photoionization detectors can continuously monitor for chemicals but cannot identify them. [4]

Aerosol photometers utilize light scattering as a detection method, and generally are lighter, more rugged, and have continuous readout relative to other direct-reading aerosol monitors. Photometers generally cannot discriminate between different types of aerosol, and background dust and water droplets can overwhelm readings for the target aerosol. For quantitative measurements, it is necessary to calibrate with an aerosol similar in refractive index and particle size to the one being measured. [7]

For chemical warfare agents, ion-mobility spectrometers, surface acoustic wave sensors, and van-mounted or portable gas chromatograph–mass spectrometers (GC/MS) may be used. [3] Portable GC/MS instruments are capable of detecting substances at the parts-per-billion to parts-per-trillion level, including narcotics, explosives, hazardous industrial chemicals, and chemical warfare agents. [8] For biological agents, some instruments can indicate the presence of biological material, such as particle analyzers, fluorometers for DNA, luminometers for ATP, and colorimeters for proteins. [3]

Sampling

OSHA TED 1-0.15A Izmerenie zagriaznionnosti vozdukha Tsiklon-1 cropped.jpg
OSHA TED 1-0.15A Izmerenie zagriaznionnosti vozdukha Passivnyi difuzionnyi probootbornik.gif
OSHA TED 1-0.15A Izmerenie zagriaznionnosti vozdukha Impindzher i barboter.gif
Three types of air sample collectors: left to right, a filter and cyclone apparatus, a diffusive sampler badge, and an impinger and bubbler

Samples may be collected through a gas sampling bag, filter, sorbent tube, or wipe. The sampling method is often chosen to match the desired analysis method. Personal air-sampling pumps pull air into a charcoal tube or filter cassette for laboratory analysis. They are more accurate than other methods, but are bulkier to wear and require more specialized knowledge to use. [1] : 49, 60–61 

Particulates

For particulates, polyvinyl chloride (PVC) filters are often used for sample collection. [2] [9] Other membrane filter materials include polytetrafluoroethylene (PTFE), copolymers, and mixed cellulose esters. Additionally, quartz or glass fiber filters may be used for mercaptans and diesel exhaust, and polycarbonate straight pore filters are suitable for electron microscopy and X-ray fluorescence analysis. [9]

The analysis method affects the type of filter used. For gravimetric analysis, non-hygroscopic materials are selected because their masses are less affected by changes in humidity. For microscopy, cellulose ester or polycarbonate membranes are preferred as the former can be rendered transparent, while the latter have a smooth collection surface. For bioaerosols collected to be cultured, gelatin filters ease transferring the samples to culture media, but are fragile. Impingers are also useful for bioaerosols as they collect samples in a liquid to avoid them losing their viability. [10]

Sampling usually distinguishes between total, inhalable, thoracic, and respirable dust. These categories correspond to how deep the particulates are deposited in the lung, with the respirable fraction being small enough to be deposited in its gas exchange region. [2] [10] The particle size selection may be determined through use of a cyclone device; as the air flow rate also affects size selection, pump calibration is important. [2] Another size selection device is an impactor, where the air stream flows through a nozzle toward an impaction surface, where larger particles impact the surface, while smaller particles are deflected and remain in the air stream. In some applications, impactors are simply used to remove larger particles before collection or characterization. For bioaerosols, they may also be used as collection devices themselves, as in an Andersen impactor where Petri dishes are directly used as the impaction surfaces. [10]

Bulk samples of suspected contaminants may be taken to compare with air samples or for additional analysis that requires more material. Field blanks may be used as a negative control to determine if contamination occurred before analysis or during sample handling, shipping, or storage. [2] [9]

Gases

For organic vapors and gases, solid sorbent sampling tubes may be used with charcoal and other sorbents as the sampling media and an active pump. [2] Activated charcoal is the most common sorbent used, with other typical sorbents including silica gel, porous polymers, synthetic carbonaceous sorbents, coated sorbents, molecular sieves, and thermal desorption tubes. [9]

Diffusive samplers, also known as passive monitors or badges, require no pump but are less accurate and sensitive. [2] These vapor monitor badges are more accurate than diffusion tubes, but must be analyzed in a laboratory, require collection of environmental conditions such as temperature and relative humidity, and are usually more expensive. Vapor monitor badges are available for a limited number of chemicals, but some that are available include formaldehyde, organic vapors, ethylene oxide, mercury, and nitrous oxide. [1] : 60 

Impingers and bubblers collect samples in a fluid; they are especially useful in high humidity environments. [2]

Gas sampling bags are often used to sample carbon dioxide, carbon monoxide, and nitrous oxide, as well as whole air samples for forensic-type investigations. [2]

Standards and regulation

Within the domain of workplace exposure monitoring, it is really important to follow certain standards and methods of doing things to make sure workers stay safe. [4] Particularly, these standards are naturally linked to the monitoring process, forming a strong foundation for safeguarding and protecting worker’s health. [11] One key aspect involves the comparison of exposure monitoring results with established health and safety guidelines. [11] This analysis acts as a checkpoint, precisely aligning exposure levels with permissible limits and indicating when corrective measures are necessary. [4] This combination of exposure monitoring with standards forms the backbone of a comprehensive approach to workplace safety. [4]

An example of this collaboration lies in the ANSI/ISEA standard 102-1990, specifically addressing gas detection tubes. These standards, created by the American National Standards Institute (ANSI) and the International Safety Equipment Association (ISEA), demonstrate the intersection of regulations and monitoring. [4] [12] The Safety Equipment Institute's third-party certification testing further solidifies this connection, ensuring the effectiveness and reliability of exposure monitoring equipment. [4] [12] It is through such standards that the monitoring process becomes a well-defined and reliable tool in supporting workplace safety. [4] [11]

As we delve into the complex landscape of workplace safety, the narrative extends globally, merging in internationally recognized organizations. OSHA (Permissible exposure limits or PELs), ACGIH (Threshold Limit Values or TLVs), NIOSH (Recommended Exposure Limits or REL), and Germany's influential MAK values are not just regulatory benchmarks; they are essential for learning about monitoring. [11] [13] Understanding these standards becomes a lens through which the monitoring process gains clarity and significance, promoting a universal language of occupational health. [4] In essence, these standards aim to ensure that workplaces worldwide adhere to the highest safety standards through an interdependent relationship between regulations and careful observation. [4] [11] They show what different groups think is safe, using different considerations.

Related Research Articles

<span class="mw-page-title-main">Personal protective equipment</span> Equipment designed to help protect an individual from hazards

Personal protective equipment (PPE) is protective clothing, helmets, goggles, or other garments or equipment designed to protect the wearer's body from injury or infection. The hazards addressed by protective equipment include physical, electrical, heat, chemicals, biohazards, and airborne particulate matter. Protective equipment may be worn for job-related occupational safety and health purposes, as well as for sports and other recreational activities. Protective clothing is applied to traditional categories of clothing, and protective gear applies to items such as pads, guards, shields, or masks, and others. PPE suits can be similar in appearance to a cleanroom suit.

<span class="mw-page-title-main">Occupational hygiene</span> Management of workplace health hazards

Occupational hygiene is the anticipation, recognition, evaluation, control, and confirmation (ARECC) of protection from risks associated with exposures to hazards in, or arising from, the workplace that may result in injury, illness, impairment, or affect the well-being of workers and members of the community. These hazards or stressors are typically divided into the categories biological, chemical, physical, ergonomic and psychosocial. The risk of a health effect from a given stressor is a function of the hazard multiplied by the exposure to the individual or group. For chemicals, the hazard can be understood by the dose response profile most often based on toxicological studies or models. Occupational hygienists work closely with toxicologists for understanding chemical hazards, physicists for physical hazards, and physicians and microbiologists for biological hazards. Environmental and occupational hygienists are considered experts in exposure science and exposure risk management. Depending on an individual's type of job, a hygienist will apply their exposure science expertise for the protection of workers, consumers and/or communities.

The permissible exposure limit is a legal limit in the United States for exposure of an employee to a chemical substance or physical agent such as high level noise. Permissible exposure limits are established by the Occupational Safety and Health Administration (OSHA). Most of OSHA's PELs were issued shortly after adoption of the Occupational Safety and Health (OSH) Act in 1970.

<span class="mw-page-title-main">Respirator</span> Device worn to protect the user from inhaling contaminants

A respirator is a device designed to protect the wearer from inhaling hazardous atmospheres including fumes, vapours, gases and particulate matter such as dusts and airborne pathogens such as viruses. There are two main categories of respirators: the air-purifying respirator, in which respirable air is obtained by filtering a contaminated atmosphere, and the air-supplied respirator, in which an alternate supply of breathable air is delivered. Within each category, different techniques are employed to reduce or eliminate noxious airborne contaminants.

Sorbent tubes are the most widely used collection media for sampling hazardous gases and vapors in air, mostly as it relates to Industrial hygiene. They were developed by the US National Institute for Occupational Safety and Health (NIOSH) for air quality testing of workers. Sorbent Tubes are available from CARO Analytical Services, SKC Inc., 7Solutions BV, Uniphos Ltd., SKC Ltd, Zefon International, Sigma-Aldrich/Supelco and Markes International. SKC Inc. manufactured the first commercially available sorbent tubes. XAD2 Tubes.

A particle counter is used for monitoring and diagnosing particle contamination within specific clean media, including air, water and chemicals. Particle counters are used in a variety of applications in support of clean manufacturing practices, industries include: electronic components and assemblies, pharmaceutical drug products and medical devices, and industrial technologies such as oil and gas.

A particulate matter sampler is an instrument for measuring the properties of particulates in the ambient air.

Exposure assessment is a branch of environmental science and occupational hygiene that focuses on the processes that take place at the interface between the environment containing the contaminant of interest and the organism being considered. These are the final steps in the path to release an environmental contaminant, through transport to its effect in a biological system. It tries to measure how much of a contaminant can be absorbed by an exposed target organism, in what form, at what rate and how much of the absorbed amount is actually available to produce a biological effect. Although the same general concepts apply to other organisms, the overwhelming majority of applications of exposure assessment are concerned with human health, making it an important tool in public health.

<span class="mw-page-title-main">Bioaerosol</span> Airborne particles containing living organisms

Bioaerosols are a subcategory of particles released from terrestrial and marine ecosystems into the atmosphere. They consist of both living and non-living components, such as fungi, pollen, bacteria and viruses. Common sources of bioaerosols include soil, water, and sewage.

Indoor bioaerosol is bioaerosol in an indoor environment. Bioaerosols are natural or artificial particles of biological origin suspended in the air. These particles are also referred to as organic dust. Bioaerosols may consist of bacteria, fungi, viruses, microbial toxins, pollen, plant fibers, etc. Size of bioaerosol particles varies from below 1 µm to 100 µm in aerodynamic diameter; viable bioaerosol particles can be suspended in air as single cells or aggregates of microorganism as small as 1–10 µm in size. Since bioaerosols are potentially related to various human health effects and the indoor environment provides a unique exposure situation, concerns about indoor bioaerosols have increased over the last decade.

Analytical thermal desorption, known within the analytical chemistry community simply as "thermal desorption" (TD), is a technique that concentrates volatile organic compounds (VOCs) in gas streams prior to injection into a gas chromatograph (GC). It can be used to lower the detection limits of GC methods, and can improve chromatographic performance by reducing peak widths.

<span class="mw-page-title-main">Aerosol mass spectrometry</span> Application of mass spectrometry to aerosol particles

Aerosol mass spectrometry is the application of mass spectrometry to the analysis of the composition of aerosol particles. Aerosol particles are defined as solid and liquid particles suspended in a gas (air), with size range of 3 nm to 100 μm in diameter and are produced from natural and anthropogenic sources, through a variety of different processes that include wind-blown suspension and combustion of fossil fuels and biomass. Analysis of these particles is important owing to their major impacts on global climate change, visibility, regional air pollution and human health. Aerosols are very complex in structure, can contain thousands of different chemical compounds within a single particle, and need to be analysed for both size and chemical composition, in real-time or off-line applications.

<span class="mw-page-title-main">Respirator fit test</span> Safety procedure for testing PPE air-tightness

A respirator fit test checks whether a respirator properly fits the face of someone who wears it. The fitting characteristic of a respirator is the ability of the mask to separate a worker's respiratory system from ambient air.

<span class="mw-page-title-main">Chemical cartridge</span> Container that cleans pollution from air inhaled through it

A respirator cartridge or canister is a type of filter that removes gases, volatile organic compounds (VOCs), and other vapors from air through adsorption, absorption, or chemisorption. It is one of two basic types of filters used by air-purifying respirators. The other is a mechanical filter, which removes only particulates. Hybrid filters combine the two.

Engineering controls are strategies designed to protect workers from hazardous conditions by placing a barrier between the worker and the hazard or by removing a hazardous substance through air ventilation. Engineering controls involve a physical change to the workplace itself, rather than relying on workers' behavior or requiring workers to wear protective clothing.

The health and safety hazards of nanomaterials include the potential toxicity of various types of nanomaterials, as well as fire and dust explosion hazards. Because nanotechnology is a recent development, the health and safety effects of exposures to nanomaterials, and what levels of exposure may be acceptable, are subjects of ongoing research. Of the possible hazards, inhalation exposure appears to present the most concern, with animal studies showing pulmonary effects such as inflammation, fibrosis, and carcinogenicity for some nanomaterials. Skin contact and ingestion exposure, and dust explosion hazards, are also a concern.

A tapered element oscillating microbalance (TEOM) is an instrument used for real-time detection of aerosol particles by measuring their mass concentration. It makes use of a small vibrating glass tube whose oscillation frequency changes when aerosol particles are deposited on it increasing its inertia. TEOM-based devices have been approved by the U.S. Environmental Protection Agency for environmental air quality monitoring, and by the U.S. Mine Safety and Health Administration for monitoring coal dust exposure for miners to prevent several respiratory diseases.

<span class="mw-page-title-main">Characterization of nanoparticles</span> Measurement of physical and chemical properties of nanoparticles

The characterization of nanoparticles is a branch of nanometrology that deals with the characterization, or measurement, of the physical and chemical properties of nanoparticles. Nanoparticles measure less than 100 nanometers in at least one of their external dimensions, and are often engineered for their unique properties. Nanoparticles are unlike conventional chemicals in that their chemical composition and concentration are not sufficient metrics for a complete description, because they vary in other physical properties such as size, shape, surface properties, crystallinity, and dispersion state.

<span class="mw-page-title-main">Titanium dioxide nanoparticle</span>

Titanium dioxide nanoparticles, also called ultrafine titanium dioxide or nanocrystalline titanium dioxide or microcrystalline titanium dioxide, are particles of titanium dioxide with diameters less than 100 nm. Ultrafine TiO2 is used in sunscreens due to its ability to block ultraviolet radiation while remaining transparent on the skin. It is in rutile crystal structure and coated with silica or/and alumina to prevent photocatalytic phenomena. The health risks of ultrafine TiO2 from dermal exposure on intact skin are considered extremely low, and it is considered safer than other substances used for ultraviolet protection.

<span class="mw-page-title-main">Mechanical filter (respirator)</span> Air-filtering face masks or mask attachments

Mechanical filters are a class of filter for air-purifying respirators that mechanically stops particulates from reaching the wearer's nose and mouth. They come in multiple physical forms.

References

  1. 1 2 3 4 5 6 7 8 Alston, Frances; Millikin, Emily J.; Piispanen, William (2018). Industrial hygiene: improving worker health through an operational risk approach. Boca Raton, FL: CRC Press. doi:10.1201/9781351131711. ISBN   978-1-351-13169-8. OCLC   1024312506.
  2. 1 2 3 4 5 6 7 8 9 "Personal Sampling for Air Contaminants". OSHA Technical Manual. U.S. Occupational Safety and Health Administration. 2014-02-11. Retrieved 2021-04-01.
  3. 1 2 3 4 5 6 7 "Technical Equipment: On-site Measurements". OSHA Technical Manual. U.S. Occupational Safety and Health Administration. 2014-02-11. Retrieved 2021-04-01.
  4. 1 2 3 4 5 6 7 8 9 10 "Portable Colorimetric Tubes for Chemical Vapor Detection: Market Survey Report" (PDF). U.S. Department of Homeland Security. 2014-05-12. pp. 1–4. Retrieved 2021-04-17.
  5. ↑ "Dräger-Tubes & CMS-Handbook, 16th edition" (PDF). Dräger Safety. 2011. pp. 22–25. Retrieved 2021-04-17.
  6. ↑ Woodfin, W. J. "Portable electrochemical sensor methods" (PDF). NIOSH Manual of Analytical Methods. U.S. National Institute for Occupational Safety and Health. Retrieved 2021-04-06.
  7. ↑ Baron, Paul A. (1998-01-15). "Aerosol photometers for respirable dust measurements" (PDF). NIOSH Manual of Analytical Methods. U.S. National Institute for Occupational Safety and Health. Retrieved 2021-04-06.PD-icon.svg This article incorporates text from this source, which is in the public domain .
  8. ↑ "Field Portable Gas Chromatograph Mass Spectrometer Instruments" (PDF). U.S. Department of Homeland Security. 2019-10-01. Retrieved 2021-04-17.
  9. 1 2 3 4 McCammon, Charles S.; Woebkenberg, Mary Lynn; Ashley, Kevin (2016-04-01). "General considerations for sampling airborne contaminants" (PDF). NIOSH Manual of Analytical Methods. U.S. National Institute for Occupational Safety and Health. Retrieved 2021-04-06.
  10. 1 2 3 Lindsley, William G.; Green, Brett J.; Blachere, Francoise M.; Martin, Stephen B.; Law, Brandon F.; Jensen, Paul A.; Schafer, Millie P. (2017-03-01). "Sampling and characterization of bioaerosols" (PDF). NIOSH Manual of Analytical Methods. U.S. National Institute for Occupational Safety and Health. Retrieved 2021-04-06.
  11. 1 2 3 4 5 McCoy, Kimberly D.; Beekmann, Susan E.; Ferguson, Kristi J.; Vaughn, Thomas E.; Torner, James C.; Woolson, Robert F.; Doebbeling, Bradley N. (2001-02). "Monitoring adherence to Standard Precautions". American Journal of Infection Control. 29 (1): 24–31. doi:10.1067/mic.2001.111226. ISSN 0196-6553
  12. 1 2 Portable Colorimetric Tubes for Chemical Vapor Detection: Market Survey Report" (PDF). U.S. Department of Homeland Security. 2014-05-12. pp. 1–4. Retrieved 2021-04-17.
  13. ↑ Hartwig, A. (2016-10-26), "Diacetyl [MAK Value Documentation, 2015]", The MAK-Collection for Occupational Health and Safety, Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA, pp. 2525–2570, retrieved 2023-11-22
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.