Monthly Archive: February 2016

NIOSH Science Blog clarifies difference between occupational and general noise exposure limits

Many people are confused about what is a safe noise limit for the general public because the only noise limit the public may have heard about is the 85 decibel recommended exposure limit (REL) that National Institute for Occupational Safety and Health (NIOSH) established for occupational noise exposures.  Fortunately, the NIOSH Science Blog has just posted an informative piece* that discusses acceptable RELS for both, titled: Understanding Noise Exposure Limits: Occupational vs. General Environmental Noise.

The authors state that in 1998, NIOSH established the REL for occupational noise exposure to be 85 decibels based on an 8-hour shift for a 5-day work week, adding that the REL “assumes that the individual spends the other 16 hours in the day, as well as weekends, in quieter conditions,” and cautioning that “the NIOSH REL is not a recommendation for noise exposures outside of the workplace in the general environment.”  The difference between the occupational and general environmental noise exposures is that:

The NIOSH REL is not meant to be used to protect against general environmental or recreational noise; it does not account for noisy activities or hobbies outside the workplace (such as hunting, power tool use, listening to music with ear buds, playing music, or attending sporting events, movies and concerts) which may increase the overall risk for hearing loss.

The authors point out that a 1974 Environmental Protection Agency (EPA) report recommended 70 decibels over a 24-hour average exposure limit for general environmental noise (while noting the EPA’s caution that its recommendation was not a standard, specification, or regulation).  This recommendation was determined in a similar manner as the NIOSH REL, but it’s focus was on general environmental noise and not the workplace.  As the EPA report states, their recommendation “was chosen to protect 96% of the general population from developing hearing loss as well as to protect ‘public health and welfare.’”

The authors note that both limits “are based on the same scientific evidence and the equal-energy rule,” but “are designed to protect against different problems.”  As a result, the limit values differ because “the EPA limit was averaged over 24 hours with no rest period while the NIOSH limit is averaged for just 8 hours and includes a rest period between exposures,” and the EPA limit includes an allowance “to protect against exposures for 365 days a year versus the NIOSH REL’s calculation that aims to protect against work place exposures for 250 working days a year.”   The authors add that “the EPA limit did not consider cost or feasibility of implementation as the Occupational Safety and Health Administration (OSHA), in accepting a NIOSH REL as the basis for a mandatory standard, [was] required to do under the Occupational Safety and Health Act of 1970.”

Long and short, the authors conclude that the 85 decibel REL is a work standard that neither mandates nor recommends decibel limits for the general public.  Rather, it is the EPA’s recommendation of 70 decibels that provides the appropriate exposure limits for the public with regard to general environmental noise.

*The post was prepared by NIOSH engineer, Chuck Kardous, MS, PE; NIOSH audiologist, Christa L. Themann, MA; NIOSH research audiologist Thais C. Morata, Ph.D., who is also the Coordinator of the NORA Manufacturing Sector Council; and W. Gregory Lotz, Ph.D, Captain, US Public Health Service, Division Director of the Division of Applied Research and Technology (DART), and the manager of the NORA Manufacturing Sector Council.

Going to the Superbowl?

Don’t forget your ear plugs! Why?  Because stadium noise is deafening and, unbelievably, encouraged.  The Kansas City Chiefs, for example, actively encourages stadium noise at Arrowhead Stadium, which the franchise boasts is the “loudest in the league.”  In 2013, a “record-setting attempt was planned by Chiefs fans but had support of the organization, which paid $7,500 to fly an adjudicator from Guinness to Kansas City to document the effort.”  They “won” with a record-breaking 137.5 decibels.  And then they did it again in 2014, this time reaching a punishing 142.2 decibels.  On purpose.  Because a lot was at stake: Kansas City Chiefs had to best the Seahawks’ loudest stadium record.  Yes, team fans compete for the glory of having the world’s loudest stadium.

While the various franchises brag about whose fans are the loudest, at least some people recognize that being the ‘world’s loudest stadium’ is a bad idea.  NBC News, reporting on the record attempt, reached out to experts to address the obvious–for some–concern about the effects of extreme noise on hearing:

What [the record-breaking attempt] is most certainly doing is damaging the hearing of every person in attendance. People don’t recognize how much damage they can do to their hearing, says Alison Grimes, an assistant clinical professor of head/neck surgery at the David Geffen School of Medicine at the University of California, Los Angeles, and director of audiology at the Ronald Reagan UCLA Medical Center.

“People will say, ‘Oh, it was just for 10 minutes,’” Grimes says. “And what I tell my patients is that noise is cumulative over the lifetime. Each time you use a chain saw or ride a motorcycle or go to a stadium to make the sound meter reach the top, it accumulates.”

While the NBC News piece sensibly suggested that fans attending the game purchase over-the-counter ear plugs, it’s likely that most of the fans who were present for this misguided attempt at glory were not protected.  Does that matter?  Will there be long-term consequences for this lapse in judgment?  Sadly, yes.  As Dr. Grimes noted:

“If you’re literally talking about 130 decibels – nobody should ever be exposed to that,” Grimes said. “There isn’t a safe amount of time for 130 decibels. It’s physically painful as well as acoustically damaging.”

Remember, “hair cells in your ear don’t grow back. There is no Rogaine for your inner ear,” warns Grimes. “While hearing aids work really well, there is no substitute for natural hearing.”

Daniel Fink, M.D., a noise pollution activist in the Los Angeles area, believes that the Kansas City organizers missed a golden opportunity to obtain recognition of another world record.  Noting that the record 142.2 dB roar exceeded the Occupational Safety & Health Administration’s (OSHA) maximum Permissible Noise Exposure of 140 dB, he suggested that the organizers should have submitted the event for a second world record: the most people whose hearing was permanently damaged at one time (about 80,000 in attendance).*

So skip the stadium and watch the Super Bowl at home.  Your ears will thank you for it.

*Dr. Fink adds that while there is no law protecting the public from the dangers of loud noise, workers have legal protection provided by OSHA.  On the day of the world record event, stadium employees and players and staff of two NFL teams were exposed to noise exceeding the maximum allowable workplace noise exposure level.  Dr. Fink filed a complaint with OSHA but was informed that the statutory limit for reporting a workplace safety violation had passed.