Urinary Biomarkers and Respiratory Responses to Indoor and Traffic-Related Air Pollution in Urban Children: A Prospective Cohort Study

Hong H.T.C. Le; Dung Phung; Phong K. Thai; Nguyen Nhu Vinh; Tran Ngoc Dang; Huynh Ngoc Thanh; Linh Le Tran; Quynh Nhat Nguyen; Hoang Thuy Dung Phan; Thi Hoai Thuong Do; Nguyen Thi Tuong Vy; Truong Thi Thuy Dung; To Thi Hien; Pham Le An

doi:10.53941/ges.2026.100025

Highlights

Study during COVID-19 lockdown offers a unique natural experiment in free traffic-related air pollution (TRAP)
Combined biomarker and lung function tests captured children’s pollution exposure
Urban children still faced harmful indoor smoke despite reduced TRAP
Urinary 1-OHP decreased after 6 months of TRAP re-exposure post-lockdown
FeNO increased in children exposed to smoke from indoor air pollution sources

Abstract

COVID-19 lockdowns unintentionally improved air quality by reducing traffic and industrial activity. This study assessed changes in respiratory health and urinary biomarkers of air pollution exposure among children with no traffic-related air pollution (TRAP) exposure and TRAP re-exposure under COVID-19-related lockdowns. A prospective cohort study was conducted with 53 children from urban districts in Ho Chi Minh City, Vietnam. Two time measurements were taken: t0 (immediately post-lockdown, no TRAP exposure) and t1 (six months after TRAP re-exposure). The children underwent physical examinations, respiratory tests (spirometry, fractional exhaled nitric oxide (FeNO)), and urine collection for 1-hydroxypyrene (1-OHP) and malondialdehyde (MDA) analysis. Overall, thirty-five children were eligible for the analysis. FeNO and lung function parameters (SVC, FVC, FEV1, FEV1/FVC) showed significant changes after TRAP re-exposure. Following the return to normal daily activities after the COVID-19 pandemic, children exposed to passive smoking exhibited lower 1-OHP levels, which may be attributable to increased time spent outdoors. Significant increases in FeNO were observed in children exposed to passive smoke (p = 0.007), incense smoke (p = 0.003), and gas cooking (p = 0.003). The respiratory function values (SVC, FVC, and FEV1) of children underwent significant increases (p < 0.05) after the lockdown was eased and their exposure to indoor pollution was reduced while being re-exposed to TRAP. Urban children remained exposed to harmful indoor pollutants despite TRAP being limited during the COVID-19 lockdown. The findings call for continued efforts to reduce air pollution exposure among children and highlight the need for further investigation into passive smoking and incense smoke.

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