The Gender Gap

To predict the likelihood of recording substantial numbers of noise-induced persistent threshold shifts, examine the demographics of your workforce.

ON July 1, 2002, the Occupational Safety and Health Administration announced a significant change in policy as it pertains to recording occupational hearing loss cases on the OSHA 300 Log. Effective January 1, 2003, OSHA's Occupational Injury and Illness Recording and Reporting Requirements (29 CFR 1904.10) defines a work-related recordable hearing loss as a change of 10 dB or greater at 2000, 3000, and 4000 Hz averaged in either ear as compared to the appropriate reference baseline audiogram (original or revised) provided that the average hearing threshold level (HTL) at those same three frequencies is 25 dB or greater.

This definition of recordable hearing loss is, of course, the same 10 dB change in hearing acuity as a Standard Threshold Shift (STS) defined by OSHA in Occupational Noise Exposure (29 CFR 1910.95). Age adjustment is permitted to determine whether an STS has been recorded, but not to determine whether the average HTL is 25 dB or greater in the same ear.

In essence, OSHA drew a line in the sand at the 25 dB hearing threshold level at 2000, 3000, and 4000 Hz averaged. A standard threshold shift recorded on an annual audiogram not resulting in an average HTL of 25 dB or greater at those same three frequencies is not a recordable event. However, an STS resulting in the average HTL equaling or exceeding 25 dB at those same frequencies now becomes an OSHA-recordable hearing loss. Work-relatedness is presumed if the employee is exposed to occupational noise levels at or above the OSHA action level (85 dB time-weighted average). Retesting within 30 days of the date of the annual test is permitted to determine persistence of the STS. An STS that is not confirmed as persistent by retest within 30 days need not be recorded (temporary threshold shift). An STS that is confirmed by retest within 30 days as a persistent threshold shift (PTS) becomes a permanent entry on the 300 Log. If a retest is not completed within the 30-day window, the STS should be recorded. However, if a subsequent retest at any later date determines the STS is no longer present (i.e., temporary threshold shift), the Log entry may be "erased or lined out." A case need not be recorded if a physician or audiologist determines the hearing loss is not work-related nor significantly aggravated by workplace noise exposure.

How the 2002 Change Came About
The 1983 OSHA Occupational Noise Exposure; Hearing Conservation Amendment; Final Rule effectively elevated hearing conservation programs to compliance status with engineering and administrative controls as a viable strategy for addressing occupational noise exposure for millions of workers. In reality, the option to implement and maintain a hearing conservation program focuses on personal hearing protection to insulate a worker from exposure to potentially noxious workplace noise.

A key component of a compliant hearing conservation program, as defined by OSHA, is the requirement to provide annual audiometric testing in order to measure and record changes in hearing sensitivity of noise-exposed workers. Annual audiometric testing provides a history of biological monitoring that can be used as a tool to gauge the overall effectiveness of a hearing conservation program, including the efficacy of personal hearing protection. Thus, employers who opted to implement hearing conservation programs in 1983 for compliance with OSHA now have 20 years of historic audiometric records. In many cases, audiometric testing programs were initiated prior to the 1983 Hearing Conservation Amendment, resulting in records dating to the 1970s and, in a few cases, even earlier.

The July 1, 2002, OSHA announcement of pending changes in policy for recording work-related hearing loss caused a good deal of anxiety for employers as they evaluated their historic audiometric records, projected the incidence of recordable hearing losses, and considered the effectiveness of hearing conservation as a noise control. Few anticipated the full impact of OSHA's new ruling as it applied to the demographic makeup of their workforce.

Impact of the Change
In calendar year 2003, HTI Inc. analyzed, professionally reviewed, and reported the results of 143,843 audiometric records gathered from manufacturing, government, and service sector employers. These audiometric evaluations were completed in mobile, on-site audiometric testing units, occupational health clinics, physicians' offices, hospital clinics, and in-plant testing programs. The results represent test data gathered throughout the contiguous United States, as well as Alaska and Hawaii.

The overall incidence of OSHA standard threshold shifts and persistent threshold shifts, both recordable and non-recordable, as a percentage of the total number of tests administered found in the 2003 records indicated that 10,260 employees recorded OSHA standard threshold shifts on their annual audiometric test. This represented 7.13 percent of the total test population and was consistent with the annual incidence of STSs historically observed by HTI. Significantly, 71.65 percent of the standard threshold shifts (7,351 employees) met the new OSHA criteria for inclusion on the 300 Log. This translated to 5.11 percent of the total test population and was considerably greater than the National Institute for Occupational Safety and Health estimate of 3.09 percent, based on NIOSH's database of audiometric records. An additional 2,909 individuals (2.02 percent of the total test population) recorded an STS that did not meet the new OSHA criteria for recordability--even though they had recorded a shift of at least 10 dB at 2000, 3000, and 4000 Hz averaged from their reference baseline audiogram.

OSHA permits, and HTI has long been a proponent of, retesting all standard threshold shifts in order to confirm or deny persistence. The case for including an individual on the 300 Log as an occupational hearing loss is substantially reinforced when the initial threshold shift pattern is confirmed by subsequent retest. When a persistent threshold shift has been recorded, professional review of the audiogram may determine whether or not the confirmed shift is a hearing loss pattern consistent with occupational noise-induced hearing loss (i.e., bilateral, symmetrical, and/or high-frequency changes in threshold values).

In 2003, of the 10,260 employees recording OSHA standard threshold shifts on their annual audiogram, 1,800 (1.25 percent of the total test population) confirmed the STS as persistent and consistent with occupational noise-induced hearing loss upon retest. Even more remarkable than the incidence of OSHA-recordable standard threshold shifts was the fact that 77.17 percent of all noise-induced persistent threshold shifts confirmed by retest met the new OSHA guidelines for inclusion on the 300 Log. That represented 0.97 percent of the total test population, resulting in essentially one employee out of every 100 tested in 2003 being an OSHA-recordable hearing loss case. This figure caught EH&S managers off guard as work-related recordable hearing losses significantly impacted their overall number of recordable OSHA cases for 2003.

Further examination of the incidence of confirmed noise-induced persistent threshold shifts by gender and age group revealed interesting and provocative patterns. The incidence of RNIPTS as a percentage of the total number of persistent noise-induced threshold shifts increased dramatically over each decade as the incidence of NIPTS decreased proportionally for both females and males. As might be predicted, 92 percent of noise-induced persistent threshold shifts for female workers and 97 percent for males 60 years of age and older met the new criteria for inclusion on the 300 Log. However, gender-specific differences in the percentage of recordable versus non-recordable noise-induced persistent threshold shift patterns were observed in the younger age groups.

The increase in the incidence of RNIPTS by age group is offset by a proportional decrease in NIPTS for both genders. However, female workers recorded a static 30 percent lower incidence of RNIPTS than men at each decade up to 60 years. Conversely, the decreased incidence of NITPS by age groups revealed the same approximate 30 percent gender difference favoring female workers up to age 60. There is also an intriguing gender-specific pattern of intersecting recordable and non-recordable noise-induced persistent threshold shifts. Male workers in the 20-29 age group recorded approximately 50 percent NIPTS and 50 percent RNIPTS. This same 50-50 split of recordable versus non-recordable noise-induced persistent threshold shifts occurred in the 40-49 age group for the female population--some 20 years later.

The static 30 percent difference in NIPTS and RNIPTS favoring female workers at each age group and the 20-year lapse between male and female populations recording 50 percent NIPTS and 50 percent RNIPTS may be explained by a combination of circumstances, as no reported studies support gender as a relevant physiological factor for predisposition to noise-induced hearing loss.

First, boys and young men are generally recognized as being vigorously involved in noisy pastimes and activities (e.g., motorized vehicles, power tools, amplified music, firearms, etc.) to a greater degree than girls and young women prior to the age when they become part of the workforce. As a result, young men entering the workforce may have already experienced a sufficient degree of noise-induced hearing loss to qualify their first occupational noise-induced persistent threshold shift for inclusion on the 300 Log. In fact, men may actually increase their pursuit of these same noisy activities after they are employed and have sufficient income to afford noisy non-occupational pastimes. Second, many young women in their twenties and thirties are actively involved as homemakers raising families and consequently take a break from or do not join the workforce until a later age, when their children are raised and college tuition and upward mobility necessitate second incomes. Therefore, many women enter the workforce full time more than a decade later than their male counterparts.

This also may account for the parallel patterns of NITPS and RNIPTS for male and female populations. Although there is a marked gender difference at each age group up to 60 and older, the incidence of NIPTS and RNITPS for females is approximately the same as for males--only occurring some 20 years later (i.e., the incidence RNITPS for 40- to 49-year-old females is approximately equal to 20- to 29-year-old males). In addition, female workers may not have a level of pre-existing hearing loss that renders their initial occupational noise-induced persistent threshold shifts as recordable. Finally, these assumptions are further supported by the combined incidence of recordable noise-induced persistent threshold shifts for women and men. Fifty-nine percent of noise-induced persistent threshold shifts recorded in all female age groups met the guidelines for inclusion on the OSHA Log, while 81 percent of male noise-induced persistent threshold shifts met the same recording criteria--a 22 percent gender difference favoring female workers.

The Challenges Ahead
Many employers were astounded and skeptical when confronted with significant numbers of OSHA-recordable noise-induced persistent threshold shifts in 2003, particularly in light of their experiences in prior years when rarely did an employee meet the former federal guidelines for inclusion on the OSHA Log (cumulative 25 dB shift at the OSHA frequencies 2000, 3000, and 4000 Hz averaged from the original baseline audiogram after age correction). The data presented in this document support the fact that employers may better predict the potential likelihood of recording substantial numbers of noise-induced persistent threshold shifts by examining the demographic makeup of their workforce.

Unfortunately, the recent decline in economic activity reported nationally throughout the manufacturing sector has resulted in downsizing and substantial numbers of furloughed employees. This, in turn, increased the age of the workforce based on seniority as older workers retained their jobs and younger workers were laid off. Many manufacturers now report that the average age of their workers is in the 50s. As demonstrated in the results shown here, an older, predominately male workforce significantly increases the likelihood that a noise-induced persistent threshold shift will also meet the new criteria for inclusion on the 300 Log.

Now, more than ever, work-related recordable hearing loss is on the radar of every production, human resource, and occupational health and safety manager. The incidence of recordable hearing loss cases has brought new focus and a sense of urgency to hearing loss prevention in the workplace. Vigorous adherence to corporate policy as it relates to proactive, compliant hearing conservation programs must be continually evaluated and rigorously enforced in light of this new, inescapable measure of program effectiveness. Whereas the incidence of NIPTS in prior years may have served as a lightly viewed statistic to gauge the overall success (or failure) of hearing conservation programs, it now carries the additional clout of increased recording activity on the OSHA Log and the associated negative stigma.

Nonetheless, the incidence of recordable noise-induced persistent threshold shifts may well be a function of the gender and age demographics of any given workforce, thus making it far more difficult to intervene and control than imagined.

This article originally appeared in the September 2004 issue of Occupational Health & Safety.

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