The potential 'blue light hazard' from LED headlamps

Richard B Price; Daniel Labrie; Braden Sullivan; David H Sliney

doi:10.1016/j.jdent.2022.104226

The potential 'blue light hazard' from LED headlamps

J Dent. 2022 Oct:125:104226. doi: 10.1016/j.jdent.2022.104226. Epub 2022 Jul 22.

Authors

Richard B Price¹, Daniel Labrie², Braden Sullivan³, David H Sliney⁴

Affiliations

¹ Department of Dental Clinical Sciences, Division of Prosthodontics, Faculty of Dentistry, Dalhousie University, 5981 University Ave., P.O. BOX 15000, Halifax, Nova Scotia B3H 4R2, Canada. Electronic address: rbprice@dal.ca.
² Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada.
³ Department of Dental Clinical Sciences, Division of Prosthodontics, Faculty of Dentistry, Dalhousie University, 5981 University Ave., P.O. BOX 15000, Halifax, Nova Scotia B3H 4R2, Canada.
⁴ Johns Hopkins University, Bloomberg School of Public Health, Baltimore, MD, USA.

PMID: 35872222
DOI: 10.1016/j.jdent.2022.104226

Abstract

Many dental personnel use light-emitting diode (LED) headlamps for hours every day. The potential retinal 'blue light hazard' from these white light headlamps is unknown.

Methods: The spectral radiant powers received from direct and indirect viewing of an electronic tablet, an LED curing light, a halogen headlamp, and 6 brands of LED headlamps were measured using integrating spheres attached to fiberoptic spectroradiometers. The spectral radiant powers were measured both directly and indirectly at a 35 cm distance, and the maximum daily exposure times (t_MAX) were calculated from the blue weighted irradiance values.

Results: The headlamps emitted very different radiant powers, emission spectra, and color temperatures (K). The total powers emitted at zero distance ranged from 47 mW from the halogen headlamp to 378 mW from the most powerful LED headlamp. The color temperatures from the headlamps ranged from 3098 K to 7253 K. The t_MAX exposure times in an 8 h day when the headlamps were viewed directly at a distance of 35 cm were: 810 s from the halogen headlamp, 53 to 220 s from the LED headlamps, and 62 s from the LED curing light. Light from the LED headlamps that was reflected back from a white reference tile 35 cm away did not exceed the maximum permissible exposure time for healthy adults. Using a blue dental dam increased the amount of reflected blue light, but t_MAX was still greater than 24 h.

Conclusions: White light LED headlamps emit very different spectra, and they all increase the retinal 'blue light hazard' compared to a halogen source. When the headlamps were viewed directly at a distance of 35 cm, the 'blue light hazard' from some headlamps was greater than from the LED curing light (t_MAX = 62 s). Depending on the headlamp brand, t_MAX could be reached after only 53s. The light from the LED headlamps that was reflected back from a white surface that was 35 cm away did not exceed the maximum permissible ocular exposure limits for healthy adults.

Clinical relevance: Reflected white light from dental headlamps does not pose a blue light hazard for healthy adults. Direct viewing may be hazardous, but the hazard can be prevented by using the appropriate blue-light blocking glasses.

Keywords: Blue light hazard; Headlamps; Light-emitting diode; Occupational hazard.

MeSH terms

Composite Resins
Curing Lights, Dental
Eye*
Halogens
Humans
Light*
Materials Testing

Substances

Composite Resins
Halogens