OSHA health hazards: silica, lead and noise for the CHST

Where these rules sit in the blueprint

Knowledge items 16 to 21 and 24 in Domain 1 cover asbestos, lead and heavy metals, noise, radiation, silica, chemicals and GHS. Domain 1 is 36.6% of the CHST. Skill item 4 asks you to pick an instrument that measures a particular hazard, so know what each hazard is measured with.

Silica: 1926.1153

Respirable crystalline silica comes from cutting, grinding, drilling and crushing concrete, masonry, stone and similar materials.

• The permissible exposure limit is 50 micrograms per cubic meter as an 8-hour time-weighted average, and the action level is 25.
• Paragraph (c) is the table of specified exposure control methods: common tasks, each paired with controls such as water or a vacuum, and a respirator level that depends on the task and its duration. An employer who follows the table fully need not measure exposure.
• An employer who does not use the table assesses exposure and follows paragraph (d).
• A written exposure control plan is required, with a competent person to carry it out, in paragraph (g).
• Medical surveillance is required for workers who must wear a respirator for 30 or more days a year, in paragraph (h).

Lead: 1926.62

• The permissible exposure limit is 50 micrograms per cubic meter over 8 hours, and the action level is 30.
• Exposure assessment is required (paragraph d), and tasks listed in the rule carry interim protection until air results are in.
• Controls follow the hierarchy (paragraph e): engineering and work practices first, respirators when those are not enough.
• Protective clothing, hygiene facilities and housekeeping are required (paragraphs g, h and i).
• Medical surveillance, with blood lead testing, applies to workers at or above the action level for more than 30 days a year (paragraph j).

Noise: 1926.52

• Table D-2 sets permissible exposure by duration, starting at 90 dBA for 8 hours. Each 5 dBA increase halves the allowed time.
• When exposure exceeds the table, the employer uses feasible engineering or administrative controls first, and hearing protection when those are not enough. See 1926.52(d)(1).
• Where exposure is above the Table D-2 limits, the employer also runs a continuing, effective hearing conservation program. See 1926.52(d)(1). The 85 dBA action level you may have seen is the general industry rule (1910.95), not the construction rule.
• Hearing protection itself is covered in 1926.101.

Asbestos and chemicals

Asbestos is regulated in 1926.1101, with its own limits, regulated areas and competent person duties. Chemical hazards use the hazard communication rule, 1926.59, which points to the general industry rule 1910.1200. That rule is built on the Globally Harmonized System, so know the label elements and the safety data sheet's role.

Common mix-ups

• Action level is not the exposure limit. It is the lower number that triggers duties like surveillance.
• Silica and lead both have a limit of 50, but their action levels differ (25 for silica, 30 for lead), and each limit applies only to its own substance.
• Table 1 is a shortcut. Following it fully replaces measurement, and following part of it does not.
• PPE is last. The hierarchy puts respirators and earplugs after elimination, substitution and engineering controls.

How to practice

Make a one-page card with each hazard, its limit, its action level and its first control. Then work questions that name a task, such as dry cutting block or grinding paint, and ask for the best control.

The noise dose and TWA arithmetic is worked step by step in the CHST formulas guide, and you can check your own numbers in the noise dose calculator.

Related guides: confined spaces and recordkeeping for medical and exposure records.

Practice it

Take the free 10-question check. It covers the four CHST domains, needs no signup and explains every answer, so you see whether this topic is a weak spot. The CHST study guide shows where it fits in a six-week plan.

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Sources

Show the list

• 29 CFR 1926 Subpart D, Occupational Health and Environmental Controls and Subpart Z, Toxic and Hazardous Substances, OSHA.
• 1926.1153, Respirable Crystalline Silica and 1926.62, Lead, OSHA.
• CHST Examination Blueprint (CHST5, V.2022.04.12), Board of Certified Safety Professionals.