Ateneo study reveals new sources of lead in Metro Manila air 

More than two decades after the phase-out of leaded gasoline in the Philippines, airborne lead remains present in Metro Manila.

A study conducted by researchers from Ateneo de Manila University, together with international collaborators, examined this persistence by analyzing fine particles in the air collected in 2018 and 2019. Using a method called lead isotope fingerprinting, they matched the chemical signatures of lead in the atmosphere to specific sources.

The findings show that, despite the removal of leaded gasoline in 2001, lead pollution has not been fully eliminated. Instead, it continues to persist through a combination of modern and residual sources that contribute to the city’s air quality.

Historically, airborne lead in Metro Manila was largely attributed to the widespread use of leaded gasoline, particularly during the rapid increase of vehicle ownership in the late 20th century. As noted in Presidential Decree No. 1181 on August 19, 1997, the growth of motorized transport in densely populated areas led to increased emissions of pollutants such as carbon monoxide, sulfur dioxide, and other associated contaminants. At the time, transportation was a major source of toxic emissions, including airborne lead.

What the researchers found, however, challenges earlier assumptions.  While leaded gasoline had long been cited as the primary source of contamination in the past, the study show today’s pollution is driven by a mix of modern and lingering factors— industrial activities particularly e-waste recycling and metal smelting now account for as much as 45 to 62% of the lead in the air. Fossil fuel use including diesel emissions and even trace elements from unleaded gasoline contributes another 30 to 45%. 

In other words, while the country successfully removed lead from fuel, other everyday activities have quietly taken its place as major sources of exposure. 

“While the data was collected in 2018 and 2019, the conclusions remain relevant today. This research highlights the importance of monitoring atmospheric lead to ensure that we do not undo the gains from phasing out leaded gasoline,” said Dr. Maria Obiminda L. Cambaliza, a physics professor at Ateneo and co-author of the study 

The findings also revealed something unique about Metro Manila: most of its lead pollution comes from within the city itself. Unlike other regions where wind patterns can carry pollutants in and out depending on the season, Metro Manila’s emissions are largely local and persistent throughout the year . This means that the problem is deeply tied to everyday urban life with factories, vehicles, and energy use that continue to power the city’s growth. 

This persistence complicates the common view of pollution as primarily a remnant of past practices. Instead, it reflects how present day urban systems—  such as transportation, energy consumption,  and industrial processes continue to produce emissions as part of their normal operation. Even with policies that have addressed major historical sources,  such as the clean air act of 1999, the structure of a highly urbanized city sustains other forms of pollution that are less visible but remain constant.

Urbanization and industrialization do not only represent growth and development but also ongoing environmental pressure. The same systems that support economic activity like factories, vehicles,  and energy use contribute to the accumulation of airborne contaminants. As a result pollution becomes embedded in the routine functioning of the city rather than confined to specific events or sources.  

Alongside the movement on productivity associated with the dance urban area like Metro Manila there is still a continuing contribution to environmental degradation. The persistence of lead in the air shows how past and present sources can overlap, with historical residues remaining while new emissions are introduced. This makes pollution not only a legacy issue, but an active and evolving condition

For residents the risks are not always visible but can be serious. Lead particles are often found in fine dust in the air small enough to be inhaled deep into the lungs and absorbed into the bloodstream. According to the World Health Organization (WHO), once inside the body lead can accumulate in organs such as the brain, liver, kidneys, and bones where it can remain for years.

The organization explains the children are especially vulnerable as they absorb lead more efficiently—up to four to five times more than adults—and their developing brains are highly sensitive to its toxic effects. As noted by the Centers for Disease Control and Prevention (CDCP),  even low levels of exposure have been linked to reduced intelligence, learning difficulties, and behavioral problems. 

Malnourished children, particularly those deficient in calcium and iron, tend to absorb higher levels of lead increasing toxicity making them face even greater risk. The CDCP notes that pregnant women are at risk because lead stored in bones can be released into the bloodstream and cross the placenta potentially affecting fetal development. They also highlight that children living in low income households or near industrial areas are more likely to experience prolonged exposure.

Despite these risks the Philippines has not updated its nationwide monitoring of lead exposure in nearly 20 years, raising concerns about how widespread the problem may be today. 

Without recent comprehensive data, public health authorities face challenges in accurately identifying the most affected communities and assessing the true extent of exposure. Regular surveillance is essential for detecting trends, guiding policy decisions, and implementing timely interventions. In the absence of updated monitoring, cases of lead exposure may go undetected or underreported particularly in vulnerable populations, limiting the effectiveness of prevention and control efforts.

Beyond gaps in monitoring, rising fuel prices and limited access to cleaner energy may push people and industries to rely more on cheaper, more polluting options leading current economic pressures to make matters worse. Poor vehicle maintenance and continued dependence on fossil fuels can further increase emissions, trapping communities in a cycle where environmental and economic challenges feed into each other. 

“There are now contemporary sources of lead, mainly from industrial activities such as e-waste processing, and fossil fuel combustion such as from diesel use and unleaded gasoline combustion. Indeed, trace amounts of lead may still come from unleaded gasoline,” Cambaliza further emphasized.

 Ultimately, the study suggests that while past policies like the phase-out of leaded gasoline in 2001 were effective, they are not enough on their own. New sources of pollution have emerged, and without continued monitoring and regulation, earlier gains could be reversed.

More than two decades after leaded gasoline was phased out, Metro Manila’s air tells a more complicated story. The progress made in the past remains significant but incomplete. As researchers point out, addressing today’s sources of pollution is just as important as eliminating those of the past, reminding people that clean air is not a one-time achievement, but an ongoing effort.