 |
||
|
||
|
Got Ear Plugs? You May Want to Sport Them on the Subway and Other Mass Transit
The U.S. mass transit system, the largest in the world, provides affordable and efficient transportation to more than 33 million riders each weekday. The system is generally considered one of the safest modes of travel, but recent public health studies have identified a number of potential environmental health hazards associated with mass transit – including excessive noise exposure.
A team of researchers from the University of Washington and the Mailman School of Public Health collaborated on the first urban mass transit noise assessment study. Although the Metropolitan Transit Authority (MTA) subways had the highest average noise levels of all mass transit in New York City, all forms of mass transit had levels in excess of Environmental Protection Agency (EPA) and World Health Organization (WHO) community guidelines, with levels high enough to potentially increase the risk of noise induced hearing loss (NIHL). Extensive noise measurements were collected from platforms and stations, as well as inside of vehicles on New York City subways (MTA and PATH), buses (MTA), ferries (Staten Island), commuter railways (LIRR, SIRR and Metro North), and the Roosevelt Island tramway.
The findings are available online in the American Journal of Public Health and will be published in the August 2009 issue.
At the Frontline spoke with Robyn Gershon, DrPH, environmental and occupational health scientist and Mailman School professor of clinical Sociomedical Sciences, principal investigator on the study, about the findings.
Q. How pervasive is the problem of noise induced hearing loss?
A. Noise induced hearing loss (NIHL) is a permanent, irreversible health problem, estimated to affect over 30 million people worldwide and as many as 10 million in the U.S. alone. Excessive noise exposure can not only cause NIHL but a wide range of other adverse health impacts as well.
Q. Did one mode of transportation stand out more than others as having the highest noise levels?
A. Yes, we found that on average, the MTA subways had the highest noise levels, at 80.4 decibels (dBA), followed by the Path trains, at 79.4 dBA, and the tram, at 77.0 dBA. The lowest average levels measured, 74.9 dBA and 75.1 dBA, were obtained from the LIRR and Metro-North trains, respectively. The very highest levels measured in the study were found on an MTA subway platform (102.1dBA) and at a bus stop (101.6 dBA).
Q. How did each of the New York City boroughs compare?
A. The borough with the overall highest mass transit noise levels was Manhattan, followed by Queens and the Bronx. In general, noise levels were significantly higher at platforms compared to inside vehicles for all forms of mass transit, except for ferries and the tram. Major hubs were noisier than local stops and underground trains and stations were significantly louder than those aboveground. But of all mass transit, subways had the highest noise levels, with roughly half of the maximum levels exceeding 90 dBA. Just as a point of reference, the noise level of a whisper is 30 dBA, normal conversation is 60 to 70 dBA, a chainsaw is 100 dBA, and gunfire is 140 dBA.
Q. Do we know how much exposure over time a NYC subway rider would need to endure to risk hearing loss?
A. At some of the highest noise levels we obtained, 102.1 dBA on the subway platforms, as little as two minutes of exposure per day would be expected to cause hearing loss in people with frequent ridership, based upon the International Organization for Standardization models for predicting hearing impairment from noise. Even at the lower average noise levels, a combined commute of roughly two hours per day, over a period of several years, will result in hearing loss for many riders.
Compared to subways, somewhat lower levels were obtained for commuter rail, buses, ferries and the tramway, however, chronic exposure to noise from these other forms of transit could also present a risk of noise induced hearing loss given sufficient exposure duration. In fact, the risk rises quickly with even small increases in noise levels. For example, 95 dBA is 10 times more intense than 85 dBA and 100 times more intense than 75 dBA.
Q. Are there government guidelines regarding recommended daily exposures to noise?
A. The U.S. Environmental Protection Agency and the World Health Organization recommend no more than 70 dBA for a 24 hour average. Noises that register below 70 dBA generally have no impact on hearing health and do not cause people to exceed the daily recommendations. One should also keep in mind that risk could increase substantially when we account for riders’ other noise exposures from work and recreational activities such as attending loud concerts, riding motorcycles or even listening to MP3 players at high volume for extended periods.
Q. Can noise affect one’s health in other ways?
A. Yes, an often overlooked fact is that in addition to impacting your hearing health, excessive noise exposure is linked to hypertension, heart disease, disruptions in stress hormones, sleep disorders, and it has been shown to adversely affect learning in children. For these reasons, it is important that noise control efforts be implemented.
Q. Is there anything we can do as individuals to reduce our transit noise exposures besides turning to automobiles?
A. Absolutely. Personal hearing protection devices can be very helpful in reducing risk. There are a variety of earplugs and earmuffs commercially available, most of which would be sufficient to reduce transit noise exposures to below the recommended limits. Just don’t be tempted to use music headphones and earbuds to block out noise; in fact, they often increase exposure, as users turn the volume of MP3 players up even higher than normal to drown out surrounding noise.
Given the fact that a loss of just 10 decibels in your hearing acuity can damage your ability to communicate, protection – and, even better, avoidance of high noise exposure when possible – is the best way to preserve your hearing.
The study, “Noise Levels Associated with New York City’s Mass Transit Systems,” was funded by the National Institute of Environmental Health Sciences. Co-authors include Marina Zeltser, Allison Canton, and Dr. Muhammad Akram.
Send to a friend | Subscribe | Unsubscribe
Mailman School Home | Columbia University Home
Copyright 2009 Columbia University Mailman School of Public Health
