Text by Charmaine A. Lingdas

Photo by Dr. Kimberly Ong

Ms. Corrine Pacheco, a clinical audiology student, performing pure tone audiometry on the MMDA employee

A recent study conducted by the researchers from the National Institutes of Health (NIH), University of the Philippines Manila (UPM) has revealed a significant correlation between occupational noise exposure and hearing problems among Metropolitan Manila Development Authority (MMDA) employees working along Epifanio de los Santos Avenue (EDSA), one of the busiest thoroughfares in Metro Manila. 

“Our study showed that 13% of the research participants experienced significant noise exposure at work, and approximately 16% of the participants had moderate hearing loss or worse on at least one ear,” said Dr. Kimberly Mae C. Ong, Research Assistant Professor at the Philippine National Ear Institute (PNEI). 

She added that EDSA traffic enforcers who were exposed to an 8-hour equivalent sound pressure level of more than 85 dBA were at least 25% more likely to experience hearing abnormalities especially at frequencies above 2000 Hz.

Dr. Ong discussed that a surprising finding was that none of the field personnel had proper equipment to protect themselves against harmful noise exposure. 

“Some of them felt that their bandana provided them sufficient protection from noise. This showed us that there is a need for hearing health education, which we hope can be integrated in their training,” Dr. Ong emphasized.

The Impact of Hearing Loss

Hearing loss is a subtle, painless, and often gradual condition. According to the World Health Organization, it is defined as the inability to hear as well as someone with normal hearing, characterized by thresholds of 20 decibels or better in both ears. It can range from mild to profound and affect one or both ears. Common causes include congenital factors, chronic middle ear infections, noise exposure, aging, and ototoxic drugs.

In mild cases, individuals may have difficulty with conversations in noisy environments, frequently asking others to repeat themselves, but usually do not experience problems in quiet settings. 

“At work, these subtle changes in hearing can affect an employee’s ability to communicate effectively with their co-workers, possibly leading to misunderstandings. It can affect productivity and work efficiency, so there is also a potential economic impact. Significant chronic noise exposure often causes irreversible hearing loss; thus, the focus should really be on hearing loss prevention,” explained Dr. Ong.

Research Respondents

Dr. Ong discussed that there are numerous studies that link noise exposure to abnormalities in hearing. Some of these were conducted in Metro Manila, which is known for its heavy traffic, and a city that ranks consistently in the top 10 most congested cities worldwide according to the TomTom Traffic Index. 

“We wanted to find out how significant road traffic noise can be in Metro Manila, and whether this can have effects on one’s hearing. We opted to focus on MMDA employees who work in traffic management, particularly those assigned to EDSA, because we felt they were more likely exposed to potentially harmful levels of noise,” said Dr. Ong.

The study, titled “Association between occupational noise exposure level and pure-tone audiometry abnormalities among Metropolitan Manila Development Authority employees: A cross-sectional study,” aimed to explore the association between noise exposure level and hearing abnormalities in any noise-exposed population.

Broader Impact

The study highlighted the importance of regular noise exposure monitoring for traffic enforcers and identifying high-risk areas for targeted noise mitigation. “Regular noise exposure monitoring should be considered especially for traffic enforcers to determine the need for noise exposure mitigation,” Dr. Ong recommended.

The findings have broader implications for other occupations exposed to road traffic noise, such as street sweepers, vendors, and public transportation drivers. Dr. Ong hopes that the results will influence public health policies and workplace safety regulations, promoting regular noise assessments, educational programs, and noise exposure control measures. “I hope this research helps to create awareness about the possible effects of prolonged noise exposure, especially to road traffic noise,” she stated.

Future Directions

The research team plans to conduct a longitudinal study to track the long-term hearing health of MMDA employees and broaden their research to include other major roads in Metro Manila. “We would like to broaden our scope and include employees assigned to other major roads in Metro Manila. Once we have more data, we can start a pilot program to evaluate the effectiveness of various noise mitigating interventions and hearing protection strategies,” Dr. Ong shared.

This groundbreaking study not only contributes to the mission of UP Manila to shape national health policies but also highlights the importance of interdisciplinary collaboration in addressing public health issues. Added Dr. Ong, “This study aligns with UP Manila’s mission to conduct integrative and collaborative applied and clinical research that can potentially shape national health policies and provide health services to the community.” 

The team of researchers was composed of the following: Dr. Ong; UP College of Medicine Dean Charlotte M. Chiong; Newborn Hearing Screening Reference Center Director Maria Rina T. Reyes-Quintos; Dr. Romeo Gian Vincent M. Urgel of the UP-PGH Department of Otorhinolaryngology; Dr. Emmanuel P. Estrella of the NIH Institute of Clinical Epidemiology, and Dr. Olivia T. Sison and Dr. Emmanuel S. Baja of the Institute of Clinical Epidemiology (ICE). The study was a collaboration between the PNEI and ICE, both under the NIH, with the cooperation of the MMDA. The National Institutes of Health fully supported the study through funding under the NIH Faculty Grant 2022.

The study was done in close coordination with the MMDA, who allowed the study to be conducted in their Main Office. It included 108 employees assigned along EDSA, with more than five years in their current positions, comprising both field and office-based personnel. Each employee wore a noise dosimeter to record noise levels during their 8-hour work shifts. Hearing tests were conducted at least 16 hours after work to avoid the effects of a hearing phenomenon known as temporary threshold shift.