# Biomarker changes before and after the 2024 peak burning period in healthy, diabetic, and hypertensive residents of Chiang Mai, Thailand

## TL;DR

Air pollution from burning in Chiang Mai increases health risks for people with diabetes and hypertension, causing higher levels of lung damage and stress markers.

## Contribution

This study is the first to examine PAH exposure and lung biomarker changes in diabetic and hypertensive individuals during seasonal burning in Chiang Mai.

## Key findings

- PAH exposure and oxidative stress markers increased significantly after the burning season.
- Diabetic participants showed larger increases in CC16, while hypertensive participants had higher 1-OHP levels.
- Some older subgroups exceeded cancer risk thresholds during the burning season.

## Abstract

Burning-related air pollution is a recurrent seasonal problem in Chiang Mai, Thailand, from March to May. Exposure has been linked to pulmonary damage and oxidative stress, measurable via serum Club Cell Protein 16 (CC16) and 8-Iso-prostaglandin F2α (8-iso-PGF2α). Polycyclic aromatic hydrocarbons (PAHs), especially 1-hydroxypyrene (1-OHP), are emitted during incomplete combustion and may contribute to diabetes and hypertension through oxidative pathways. Few studies have examined how PAH exposure from seasonal air pollution affects lung function biomarkers in individuals with these conditions in this region.

A prospective cohort study was conducted in three Chiang Mai locations, following 127 participants with diabetes and/or hypertension during the before-burning (December 2023) and after-burning (May 2024) periods. Urinary 1-OHP measured PAH exposure, while serum CC16 and 8-iso-PGF2α assessed pulmonary damage and oxidative stress. Structured questionnaires captured participant characteristics and symptoms. Quantitative health-risk assessment (QHRA) converted 1-OHP to benzo[a]pyrene-equivalent doses for estimating lifetime cancer risk (LCR) and hazard quotient (HQ).

From before- to after-burning, cohort-wide means increased significantly: urinary 1-OHP (0.24 ± 0.05 to 0.90 ± 1.21 μmol/mol Cre; p < 0.01), serum CC16 (63.15 ± 25.74 to 101.31 ± 48.14 ng/ml; p < 0.01), and serum 8-iso-PGF2α (47.44 ± 19.91 to 52.51 ± 20.56 ng/ml; p < 0.01). Stratified by comorbidity, hypertensive participants showed a greater 1-OHP increase (0.25 ± 0.35 to 1.31 ± 1.67; p < 0.01), while diabetic participants had larger CC16 rises (62.39 ± 18.96 to 93.23 ± 29.92; p < 0.01). Among diabetics in the after-burning period, those reporting skin irritation or shortness of breath had lower urinary 1-OHP than asymptomatic peers (0.50 vs. 1.14 and 0.48 vs. 1.08 μmol/mol Cre; p = 0.049 and 0.036, respectively). QHRA showed that during the burning season, several age–sex–disease subgroups exceeded the 1 × 10−4 LCR benchmark, notably men ≥50 years and some women >60 years, while all HQs remained < 1.

After burning in Chiang Mai substantially increases PAH exposure, pulmonary injury markers, and oxidative stress in individuals with diabetes and hypertension, with differential effects by comorbidity. Cancer risk thresholds were exceeded in older subgroups despite HQs below non-cancer hazard levels, highlighting the need for targeted protection strategies during burn seasons.