Naphthalene (91-20-3)
Naphthalene is a aromatic hydrocarbon with CAS Registry Number 91-20-3. Under the OSHA air contaminants standard (29 CFR 1910.1000), its Permissible Exposure Limit (PEL) — the legal 8-hour time-weighted average (TWA) for general industry — is 10 ppm. The principal target organs are the Eyes; blood; liver, and workplace air is sampled and analyzed by NIOSH 1500.
Exposure Limits at a Glance
| Limit | Value | Basis |
|---|---|---|
| OSHA PEL (8-hr TWA) | 10 ppm | 29 CFR 1910.1000 |
| NIOSH REL | See note below | NIOSH Pocket Guide |
| Hazard Class | Aromatic Hydrocarbon | Aromatic |
| Target Organs | Eyes; blood; liver | NIOSH / OSHA |
| Sampling Method | NIOSH 1500 | NIOSH Manual of Analytical Methods |
NIOSH REL note: NIOSH RELs are typically far more protective (e.g. benzene 1 ppm PEL vs 0.1 ppm REL). The REL is a non-regulatory recommendation; where a NIOSH REL exists it is typically more protective than the OSHA PEL.
How It Enters the Body & Health Effects
Exposure to Naphthalene is assessed against the Eyes; blood; liver — the organ systems most consistently affected in occupational studies. Employers must ensure no employee’s 8-hour TWA exceeds the 10 ppm PEL, and must use engineering controls, work practices, and — where required — respiratory protection to keep exposures at or below that level.
- Hazard class: Aromatic Hydrocarbon. Aromatic-class agents are managed with the hierarchy of controls (elimination, substitution, engineering controls, administrative controls, then PPE).
- Monitoring: collect personal air samples in the breathing zone and submit them under NIOSH 1500 for laboratory analysis.
- Medical surveillance: consult the OSHA substance-specific standards and the NIOSH Pocket Guide when the target organs are the Eyes; blood; liver.
Sampling & Compliance Notes
- Determine whether the exposure is a full-period 8-hour TWA or a short-term / ceiling scenario. Ceiling and STEL excursions apply to several Aromatic-class agents regardless of the 8-hour average.
- Calibrate personal sampling pumps before and after each shift and record flow rates; method NIOSH 1500 specifies media, flow, and analysis.
- Compare analytical results to the OSHA PEL of 10 ppm and the NIOSH REL. Document the higher of the two for internal exposure-control targets.
- Where the PEL includes a “skin” notation, dermal absorption can contribute to the dose — glove selection and hygiene facilities are part of compliance.
Frequently Asked Questions
What is the OSHA PEL for Naphthalene?
The OSHA Permissible Exposure Limit (8-hour TWA) for Naphthalene is 10 ppm.
What is the CAS number for Naphthalene?
The CAS Registry Number for Naphthalene is 91-20-3.
What are the target organs for Naphthalene?
The primary target organs are the Eyes; blood; liver.
How do you measure Naphthalene in workplace air?
Use NIOSH analytical method NIOSH 1500 for air sampling and laboratory analysis.
What hazard class is Naphthalene?
It is classified here as a Aromatic Hydrocarbon (Aromatic).