Many general dental offices in the U.S. operate with fewer than 10 employees, which makes them exempt under OSHA’s recordkeeping rules from maintaining injury and illness logs (per 29 CFR §1904). Simultaneously, these offices often work with elemental mercury in the form of placing and/or removing dental mercury amalgam fillings — an established neurotoxin with well-documented occupational risks.

This creates a circular logic flaw:

  • Despite widespread use of mercury in dentistry, OSHA classifies dental practices as a low hazard industry (NAICS code 621210).
  • The vast majority of dental offices have fewer than 10 employees and thus are not required to report or track injuries or illnesses.
  • Therefore, data on harm is systematically underreported or never collected, reinforcing the incorrect assumption of dental offices as a low hazard industry.

Magnitude of the Problem: Dental Employees at Risk

  • There are approximately 372,000 dental assistants in the U.S. (BLS, May 2023), and 96% of them are female—a group largely of childbearing potential.
  • Additionally, there are about 214,000 Registered Dental Hygienists (RDHs) in the U.S. (BLS, May 2023), with approximately 94% being female (201,000). Among RDHs, an estimated 70% (approximately 150,000) may come into contact with elemental mercury during amalgam polishing procedures, depending on the practice setting and frequency of amalgam use.
  • Among the 160,600 general dentists in the U.S., an estimated 70,000 are employees (non-owners). Approximately 48.3% of these employee dentists are female, totaling about 33,800 women.
  • Combined, there are over 656,000 dental employees—dental assistants, RDHs, and employee general dentists — who may be occupationally exposed to elemental mercury in clinical settings.
  • Approximately 47,000 dental assistants and an estimated 25,000 Registered Dental Hygienists (RDHs) work in corporate Dental Service Organizations (DSOs) with more than 10 employees, while the remaining ~325,000 assistants, ~189,000 RDHs, and approximately 63,000 associate dentists (out of an estimated 70,000 employee general dentists) are likely employed in small, non-corporate practices—many of which, with 10 or fewer employees, but remain exempt from OSHA injury and illness reporting due to their size.

Regulatory Blind Spots Reinforced by Policy Incentives

The Department of Labor’s July 2025 policy revisions expand penalty reductions for small employers, which—while well-intentioned—may further disincentivize rigorous hazard abatement in small dental settings. Previously, a 70% penalty reduction was limited to businesses with 10 or fewer employees, but that threshold now extends to employers with up to 25 employees. Many dental offices fall within this range, and will now benefit from reduced penalties even when citations are issued.

Additional discounts—such as a 15% reduction for employers who take immediate corrective action and a 20% reduction for employers with no inspection history or no prior serious violations—can compound to significantly lower fines. These incentives, while designed to encourage compliance, may also enable systemic underreporting and under-correction of serious hazards like mercury exposure in environments already excluded from basic OSHA surveillance and reporting requirements.

A Hidden Reproductive Hazard

Given that Safety Data Sheets (SDSs) for mercury identify fetal death and developmental toxicity as possible outcomes, exposure to dental mercury is not just a risk to the worker—but to any developing fetus if the employee becomes pregnant. Despite this, OSHA does not require substance-specific monitoring or medical surveillance for mercury, leaving hundreds of thousands of frontline dental workers—especially assistants—vulnerable to toxic exposures without mandated surveillance, documentation, or regulatory scrutiny.

Update 07/14/2025: US Department of Labor updates penalty guidelines to support small businesses & eliminate workplace hazards