Maintaining and revising baseline audiograms

If employees are exposed to excessive noise at work, employers must establish a baseline audiogram no later than six months after the first exposure. OSHA does provide a “mobile van test exception” allowing up to one year, if employees wear hearing protection in the interim. Remember that “exposure” means even one day above the action level.

The first exposure is usually the first day of work in an area with noise above the action level. However, current employees may get transferred in or out of a noisy area. Also, employers might rehire former workers, raising questions about whether to establish a new baseline.

Transferred workers

If a worker transfers out of a noisy area, the employer may remove the worker from the hearing conservation program after one year of no exposure above the action level. OSHA addressed this in an interpretation dated February 13, 2004.

However, employers must retain that worker’s baseline audiogram for the duration of employment. If that worker later transfers back to a noisy area, OSHA does not allow establishing a new baseline. Doing so would be considered revising the baseline. Any future hearing tests must be compared to the original baseline. OSHA addressed this in an interpretation dated January 31, 2011.

There is no period of time after which baseline becomes invalid. Even if someone works several years in another position before re-entering a job with noise exposure, employers must use original baseline.

Rehired workers

Rehired workers are treated much the same as transferred employees. If a former employee is rehired and the employer still has the original baseline, that audiogram should remain in use as the baseline. OSHA addressed this in an interpretation dated February 8, 2005.

Again, a baseline audiogram does not “expire” after a certain time. However, if the audiograms from prior employment were not retained, then the first valid audiogram taken after rehire would become the baseline.

Somewhat related, OSHA also addressed successor employer obligations, like when one company acquires or buys another company. The successor employer cannot establish new baselines for employees. The successor should receive records from the prior employer and must continue to use those baselines. OSHA addressed this in an interpretation dated March 8, 2011.

Revising baselines

So when can employers revise the baseline audiogram? If an employee experienced a Standard Threshold Shift (STS) that is persistent, OSHA allows revising the baseline by substituting that annual audiogram. One reason is to avoid continually recording the same STS in future years. OSHA addressed this in an interpretation dated May 8, 2003.

The baseline must be revised for each ear separately. An employee might experience an STS is one ear, perhaps due to improperly using hearing protection on that side, or because a noise source is consistently on one side. If that employee later gets anSTS in the other ear, the employer must take appropriate actions, and may then also revise the baseline for that ear.