Canadian Occupational Exposure Limits

Provinces differ in three main ways: where the numbers come from, which edition of the ACGIH list applies, and the extra rules for short peaks, long shifts and mixtures. Some use the current ACGIH Threshold Limit Values (TLVs). Some freeze an older ACGIH edition. Others publish their own table. As a result, the same substance can have very different limits. For benzene, Ontario's table shows an 8-hour average (TWA) of 0.5 ppm. Newfoundland and Labrador expected employers to use ACGIH's 2024 TWA of 0.02 ppm from September 30, 2024.

Approach: I tried the Ontario Reg. 833, Alberta Schedule 1, WorkSafeBC Part 5, CCOHS and GESTIS datasets, but none of them returned results this time. Everything below comes from official legislation portals and regulator pages I opened. For Québec, the territories and New Brunswick's current edition I had to rely on the CCOHS legislation summary.

1. Where the limit values come from

Model	Jurisdiction	What the text says
Current ACGIH list, updated as ACGIH changes it	Federal (COHSR s. 10.19, current to 2026-10-19)	ACGIH value "as amended from time to time"; grain dust 4 mg/m³, flour dust 3 mg/m³ (Justice Laws)
	British Columbia (s. 5.48)	ACGIH ceiling, short-term (STEL) or 8-hour TWA limit, "except as otherwise determined by the Board" (WorkSafeBC Part 5)
	Nova Scotia (s. 2.3)	"the latest version" of the ACGIH TLVs and BEIs, amended through N.S. Reg. 163/2025 (NS regulation)
	Newfoundland and Labrador (s. 42(7)(d))	The regulations "automatically adopt" ACGIH TLVs (NL advisory)
	Prince Edward Island (s. 11.3)	ACGIH "2019 edition… as amended from time to time", applied through a ventilation duty (PEI regulation, current to January 1, 2025)
A fixed older ACGIH edition	Ontario	The Ontario Table first; for agents not on it, the 2017 ACGIH Table (Ontario, updated June 26, 2025)
	Manitoba (M.R. 217/2006, Part 36)	Employers "must establish" their own limits, which "must not exceed" the 2019 ACGIH TLVs (Manitoba)
	New Brunswick	CCOHS (July 2022) says the 1997 ACGIH edition, General Regulation ss. 23-25 (CCOHS). The provincial portal wouldn't open, so I couldn't confirm whether a 2022 amendment changed the edition.
The jurisdiction's own table	Alberta	Schedule 1, Table 2 (OHS Code s. 16)
	Saskatchewan	Table 18 "Contamination Limits" (Regulations, 2020, s. 21-6)
	Québec	Schedule I of the Regulation respecting occupational health and safety (per CCOHS)
	Yukon	Tables 8 to 15, s. 27 (per CCOHS)
	Northwest Territories, Nunavut	Schedules O, Q and R (per CCOHS)

Why this matters: in January 2024, ACGIH lowered the benzene TWA to 0.02 ppm, removed the STEL and added a skin notation. Newfoundland and Labrador said all employers "should be utilizing" the new limit from September 30, 2024. Ontario's table still shows benzene at a TWA of 0.5 ppm and a STEL of 2.5 ppm (skin). Jurisdictions tied to a fixed edition or their own table only change when their own text is amended.

2. Short peaks when only an 8-hour limit is listed

• BC (s. 5.49): no more than 3 times the TWA for a total of 30 minutes in the work period, and never 5 times the TWA.
• Alberta (s. 16(4)): no more than 3 times the 8-hour limit for a total of 30 minutes in a continuous 24-hour period, and never 5 times that limit. If the level immediately dangerous to life and health (IDLH) is lower, it applies instead (Alberta Part 4). Ceiling limits may not be exceeded "at any time" (s. 16(3.1)).

3. Shifts longer than 8 hours

• BC (s. 5.50): fixed reduction factors for the TWA:
  • 0.7 for more than 8 and up to 10 hours
  • 0.5 for more than 10 and up to 12 hours
  • 0.25 for more than 12 and up to 16 hours
  • 0.1 for more than 16 hours
• Alberta (s. 18): the employer "must" multiply the 8-hour limit by a daily reduction factor based on hours worked. This does not apply to substances marked "3" in the Substance Interaction column. Another scientific method approved by a Director may be used instead.
• Saskatchewan (s. 21-6(2)-(4)): no factor is set. The employer must write and follow a procedure if workers regularly work more than 8 hours a day or 40 hours a week (Saskatchewan regulation, pp. 166-167).
• Ontario: the ministry page points to an adjustment tool for irregular shifts based on the "Quebec model".

4. Mixtures

• BC (s. 5.51): combined exposure to substances with similar effects must not exceed 100%.
• Alberta (s. 17): for substances with similar modes of toxic action, the combined total D must not exceed 1.
• Saskatchewan (s. 21-6(2)(b)): a written procedure is required for combinations with similar effects on the same organ or body system.

5. How strict the duty is, and carcinogens

• Alberta: exposure to any listed substance must be kept "as low as reasonably achievable" (s. 16(1)). Substances with no limit get the same duty (s. 16(3)).
• BC (s. 5.57): carcinogens, reproductive toxins and sensitizers must be substituted where practicable.
• Manitoba: limits for carcinogens, respiratory sensitizers, reproductive toxins and mutagens "must be as close to zero as possible".
• Federal (s. 10.19(1.1)): asbestos must be "as close to zero as possible".
• Saskatchewan:
  • The duty is framed as engineering controls "to the extent that it is reasonably practicable", plus "all practicable steps" to keep personal exposure within Table 18 (s. 21-6(1)).
  • A respirator is required where reduction is not reasonably practicable (s. 21-8).
  • Table 16 substances need the director's written permission (s. 21-4).

Not confirmed this time

• Québec: the Légis Québec server would not open (official link), so I don't have its excursion or shift-adjustment wording.
• New Brunswick: I couldn't confirm the current ACGIH edition.
• Territories: covered only by the 2022 CCOHS summary.
• Substance values: I couldn't pull specific numbers from the Alberta Schedule 1 or WorkSafeBC tables.

If you name a substance, I can try again to put the values side by side for each jurisdiction.

Canadian limits are generally stricter than federal OSHA limits, and the gap is often large. OSHA says most of its permissible exposure limits (PELs) "were issued shortly after adoption of the Occupational Safety and Health (OSH) Act in 1970, and have not been updated since," and that many are "outdated and inadequate" (OSHA). Canadian jurisdictions instead follow ACGIH values, either current or a recent edition, or their own updated tables. For example, Ontario's toluene limit is 20 ppm against OSHA's 200 ppm, and its n-hexane limit is 50 ppm against OSHA's 500 ppm.

Approach: I couldn't check the OSHA Z-table and Canadian limit-table datasets this time, so the comparison comes from OSHA's 29 CFR 1910 standards, OSHA's annotated PEL tables and Ontario's Reg. 833 limits page. The Canadian rules on shifts, mixtures and edition dates are from the official pages cited in my last two answers.

Side by side for six common substances (8-hour TWA unless noted)

Substance	Federal OSHA PEL	Cal/OSHA PEL (as of 11/12/2021)	NIOSH REL (advisory)	Ontario (Reg. 833)
Benzene	1 ppm; STEL 5 ppm (1910.1028)	See Cal/OSHA s. 5218	0.1 ppm; ST 1 ppm	0.5 ppm; STEL 2.5 ppm; skin
Formaldehyde	0.75 ppm; STEL 2 ppm (1910.1048)	See Cal/OSHA s. 5217	0.016 ppm; C 0.1 ppm	STEL 1 ppm; C 1.5 ppm
Toluene	200 ppm; ceiling 300 ppm; peak 500 ppm for 10 min (Table Z-2)	10 ppm; ST 150 ppm; C 500 ppm	100 ppm; ST 150 ppm	20 ppm
n-Hexane	500 ppm	50 ppm	50 ppm	50 ppm; skin
Acetone	1000 ppm	500 ppm; ST 750 ppm; C 3000 ppm	250 ppm	250 ppm; STEL 500 ppm
Carbon monoxide	50 ppm	25 ppm; C 200 ppm	35 ppm; C 200 ppm	25 ppm

Sources: OSHA annotated Table Z-1, annotated Table Z-2, 1910.1028, 1910.1048, and the Ontario limits page (updated June 26, 2025).

What the table shows:

• Most solvents and gases: the Ontario value is 2 to 10 times lower than the federal OSHA PEL, and it often matches the NIOSH value or the Cal/OSHA value.
• Benzene: Ontario is half the OSHA limit. Under the 2024 ACGIH value (0.02 ppm), which Newfoundland and Labrador expected employers to use from September 30, 2024 (see my last answer), the gap is about 50 times.
• Formaldehyde: the comparison is not one-directional. OSHA has an 8-hour TWA of 0.75 ppm and a STEL of 2 ppm. Ontario lists no TWA, but has a STEL of 1 ppm and a ceiling of 1.5 ppm.
• Grain dust: the OSHA PEL is 10 mg/m³, against the federal Canadian COHSR value of 4 mg/m³ (s. 10.19).

How the systems differ in structure

Where the numbers come from

• US: PELs are fixed in regulation (Tables Z-1, Z-2 and Z-3 of 29 CFR 1910.1000), plus separate standards for substances such as benzene and formaldehyde.
• OSHA's own advice: OSHA prints Cal/OSHA and NIOSH values next to its PELs. It also links each substance to its ACGIH TLV, but doesn't show the TLV values because ACGIH holds the copyright. OSHA "recommends that employers consider using the alternative occupational exposure limits" because exposures above them "may be hazardous to workers, even when the exposure levels are in compliance with the relevant PELs" (OSHA).
• Canada: ACGIH is built into the law itself. Federal COHSR, BC, Nova Scotia and Newfoundland and Labrador follow the current ACGIH TLVs. Ontario and Manitoba fix a 2017 or 2019 ACGIH edition. Alberta, Saskatchewan and Québec publish their own tables. For substances on Canadian lists, a binding Canadian limit is usually closer to the TLV than the federal OSHA PEL is.

US states

• States that run their own OSHA-approved programs can set stricter values. Cal/OSHA is the example in OSHA's annotated tables, with lower limits than federal OSHA for every substance in the table above that has a figure (benzene and formaldehyde point to separate Cal/OSHA sections). This is a similar split to the provincial patchwork in Canada.

Peaks and ceilings

• OSHA (1910.1000(a)): a value marked "C" "shall at no time" be exceeded; other values are 8-hour TWAs "in any 8-hour work shift of a 40-hour work week." Table Z-2 also allows brief peaks above the ceiling within set limits (toluene: 500 ppm for 10 min).
• BC (s. 5.49) and Alberta (s. 16(4)): where only an 8-hour value is listed, exposure must not exceed 3 times that value for more than 30 minutes in total (in the work period in BC; in any 24-hour period in Alberta), and never 5 times it.

Mixtures

• OSHA uses an additive formula, Em = C1/L1 + C2/L2 + … + Cn/Ln, and Em must not exceed 1 (1910.1000(d)).
• This is the same approach as BC s. 5.51 (100% in total) and Alberta s. 17 (D not above 1).

Long shifts

• The 1910.1000 provisions I read set no adjustment for shifts longer than 8 hours.
• BC (s. 5.50) and Alberta (s. 18) require reduction factors for longer shifts. Saskatchewan requires a written procedure instead.

Controls

• OSHA requires administrative or engineering controls "first" where feasible, and protective equipment where those cannot achieve compliance (1910.1000(e)).
• Canadian rules add stronger duties for some substances:
  • Alberta: exposure must be kept "as low as reasonably achievable".
  • BC: carcinogens, reproductive toxins and sensitizers must be substituted where practicable.
  • Manitoba: limits for carcinogens and similar substances must be "as close to zero as possible".

Action levels

• OSHA's substance-specific standards add action levels: 0.5 ppm for both benzene and formaldehyde. These trigger further requirements below the PEL.

I can do the same comparison for Alberta, BC or Québec, or for a substance you name.