Occupational Hygiene Sampling and Exposure Limits by Rachel Pinto (Mhsc, CIH), Occupational Hygienist, University of Guelph

Occupational

Hygiene Sampling

and Exposure Limits

For Veterinary Practices

Disclaimer

The following material has been prepared for the information of members of the Ontario Veterinary Medical Association as a guideline only relating to various safety issues encountered at a veterinary practice. In all cases, it is the responsibility of individual veterinarians to ensure that their practices and standards comply with all applicable federal, provincial, and municipal by-laws, regulations, and legislation. Nothing contained in this guide suggests or implies complete or proper training or certification of veterinarians or their staff as might be required by legislation.

Occupational Hygiene Sampling and Exposure Limits By Rachel Pinto (MHSc, CIH), Occupational Hygienist, University of Guelph

What is occupational hygiene? Occupational hygiene, often also referred to as industrial hygiene, is an aspect of health and safety dedicated to the anticipation, recognition, evaluation and control of workplace hazards, to prevent the onset of occupational disease.

Workplace hazards may be physical (e.g., noise, radiation), chemical (e.g., anesthetics, chemotherapy drugs, disinfectants, formalin), biological (e.g., zoonotic agents) or ergonomic agents (e.g., lifting patients).

Anticipating and recognizing hazards involves reviewing workplace tasks, processes and equipment to identify hazards and stressors that may be present in the workplace.

Evaluating workplace hazards involves assessing the degree of risk the hazard poses to the health and safety of workers and often includes taking measurements or conducting occupational hygiene sampling.

Prevention and control of exposure involves eliminating hazards or substituting work processes or tasks with less hazardous options, or implementing engineered solutions (e.g., local exhaust ventilation), administrative controls (e.g., warning signs, standard operating procedures), or the use of personal protective equipment (e.g., respirators, gloves).

What is occupational hygiene sampling? Air sampling for gases, vapours, particles or biological materials; sound level monitoring; or measurements related to thermal stress, radiation or ergonomics are all considered occupational hygiene sampling.

Occupational hygiene sampling is typically conducted when there is a concern about workplace exposures to an agent or if there is a legal requirement to quantify exposures in the work environment. The objective of occupational hygiene sampling is to obtain a representative measurement of employee exposure to an agent.

Occupational hygiene sampling is conducted by an occupational hygienist, occupational hygiene technologist or a person trained in the use of occupational hygiene sampling instrumentation and methods.

Occupational hygiene air sampling involves collecting an airborne substance on sampling media during part of or for a full work shift, passively or using a pump. Sampling must be conducted in accordance with validated methods, developed for the particular agent. For chemical substances, methods are typically from the National Institute of Occupational Safety and Health (NIOSH) Manual of Analytical Methods or the Occupational Health and Safety Administration Salt Lake

City Laboratory. Analysis must be conducted by an American Industrial Hygiene Association (AIHA) accredited laboratory that has demonstrated proficiency in these analytical methods. Occupational hygiene sampling for some substances can be carried out using a direct-reading instrument, where airborne concentrations are electronically logged and/or displayed on the instrument in real time.

In veterinary settings, agents that are often sampled include radiation due to use ofx-ray technology, formaldehyde, glutaraldehyde, waste anesthetic gases, dusts from feeds and bedding, allergens and bioaerosols in bedding, cleaning chemical vapours, and noise due to animal noise (e.g., barking dogs, squealing pigs).

What are workplace exposure limits? Workplace exposure limits, also called occupational exposure limits (OELs) are upper thresholds for a substance or agent, in the workplace. They represent levels to which it is believed nearly all workers may be exposed without adverse effects. OELs are set and enforced by government agencies to protect worker health. Results obtained from occupational hygiene sampling are compared to OELs to assess compliance and determine if additional controls are required to protect workers from the hazard.

OELs are prescribed in multiple regulations under the Ontario Occupational Health and Safety Act (OHSA). The regulations also reference OELs in guidelines and standards from other government agencies. There are chemical and biological agents for which OELs have not been established due to insufficient scientific data. For these substances, and in general, regardless of the existence of an established and or prescribed OEL, occupational exposures should be maintained as low as reasonably achievable.

It should be noted that OELs are not to be regarded as a line between safe and unsafe conditions, but rather an enforceable legal limit. In Ontario, employers are required to take all reasonable precautions for the protection of a worker (OHSA s. 25 (2) h) and take all measures reasonably necessary in the circumstances, to protect workers from exposure to a hazardous biological or chemical agent because of the storage, handling, processing or use of such agent in the workplace (Ontario Regulation 833 s. 3(1)).

There are three commonly referenced OELs for chemical substances: time-weighted average (TWA), short-term exposure limit (STEL) and ceiling limit (C). The TWA is the average airborne concentration of a biological or chemical agent to which a worker may be exposed in a work day or a work week. The STEL is maximum airborne concentration of a biological or chemical agent to which a worker may be exposed in any 15-minute period. The C is the maximum airborne concentration of a biological or chemical agent to which a worker may be exposed at any time. There are OELs for over 725 substances referenced in Ontario Regulation 833 (O. Reg. 833/90) Control of Exposure to Biological and Chemical Agents and Ontario Regulation 490 (O. Reg. 490/09) Designated Substances, under the OHSA.

Under Ontario 381 (O. Reg. 381/15), the OEL for noise is an 8-hour TWA of 85 dBA also referred to as the equivalent sound exposure level or Lex,8. dBA means a sound level in decibels using a reference sound pressure of 20 Pascals when measured in the A-weighting network of a sound level meter.

OELs for thermal stress, ergonomics and radiation are not directly referenced in the OHSA and associated regulations, but are available in national and international standards, guidelines and legislation.

Additional Resources

American Conference of Governmental Industrial Hygienists (ACGIH). https://www.acgih.org/home

American Industrial Hygiene Association (AIHA). https://www.aiha.org/about-ih/I-am-IH/Pages/I-am-IH.aspx

Canadian Centre for Occupational Health and Safety (CCOHS). Occupational Hygiene – Occupational Exposure Limits. https://www.ccohs.ca/oshanswers/hsprograms/occ_hygiene/occ_exposure_limits.html

Occupational Health Clinics for Ontario Workers Inc. (OHCOW). https://www.ohcow.on.ca/

Occupational Hygiene Association of Ontario - Consultants Directory. https://www.ohao.org/index.php/consultantsdirectory

Occupational Safety and Health Administration (OSHA). Information Booklet on Industrial Hygiene. https://www.osha.gov/Publications/OSHA3143/OSHA3143.htm

Ontario Ministry of Labour. A Guide to the Noise Regulation (O. Re. 381/15) under the Occupational Health and Safety Act. https://www.labour.gov.on.ca/english/hs/pubs/noise/

Ontario Ministry of Labour. Occupational Exposure Limits. https://www.labour.gov.on.ca/english/hs/topics/oels.php

Disclaimer The information expressed herein does not purport to reflect the opinion or view of the University of Guelph. The article was written by a health and safety professional with background, training and experience in occupational, health and safety. Every effort is made to provide accurate and current information on the topic, but the author disclaims any liability, loss or risk resulting directly or indirectly from the use of the information presented. It is incumbent on workplace parties to consult applicable local, provincial and federal laws, regulations to ensure compliance with legislation.

Acknowledgements I would like to gratefully acknowledge Mary Fowler, RVT, Grant Maxie, DVM, PhD, Diplomate ACVP, Manuela Racki, PEng, CRSP, EP, and Nancy E. Wilk, HBSc, MHSc, CIH, who reviewed these articles and provided valuable feedback.