Indoor exposure to heavy metals poses human health risks worldwide, but study reports from Thailand are still limited, particularly in rural and urban areas. We measured the heavy metals in a hundred indoor household dust samples collected from urban and rural areas in Chiang Mai and Lamphun provinces and found a significantly higher concentration of As in rural areas and Cd in urban areas with industrial activities. The source identification of the heavy metals showed significant enrichment from traffic emissions, paint, smoking, and mixed sources with natural soil. From health risk assessment models, children were more vulnerable to noncarcinogenic risks (HI = 1.45), primarily via ingestion (HQ = 1.39). Lifetime cancer risks (LCRs) due to heavy metal exposure were found in adults (LCR = 5.31 × 10⁻⁴) and children (LCR = 9.05 × 10⁻⁴). The cancer risks from As were higher in rural areas via ingestion, while Cr and Ni were higher in urban areas via inhalation and ingestion, respectively. This study estimated that approximately 5 out of 10,000 adults and 9 out of 10,000 children among the population may develop cancer in their lifetime from exposure to indoor heavy metals in this region.

Heavy metals are significant environmental pollutants that are recognized as posing a potential health hazard to human beings. We investigated the concentrations of the heavy metals As, Cd, Cr, Cu, Ni, Pb, and Zn in surface sediments collected from the Mae Chaem River in Chiang Mai, Thailand, during the dry season in 2021. The mean concentrations of heavy metals in sediments were, in decreasing order, Zn > Cr > As > Pb > Ni > Cu > Cd. The mean values of As, Cd, Cr, and Cu were determined to be 32.5 ± 18.3, 0.33 ± 0.07, 45.8 ± 11.9, and 21.9 ± 7.42 mg Kg⁻¹, respectively. These levels are higher than their standard levels in Thailand, namely 10.0, 0.16, 45.5, and 21.5 mg Kg⁻¹, respectively. Principal component analysis (PCA) revealed that the primary origins of heavy metal contamination are predominantly attributed to residential settlements and agricultural areas. The hazard quotient (HQ) was used to estimate the non-carcinogenic risk of exposure to heavy-metal-bound surface sediments for both children and adults. The results showed that the HQ values for both groups were less than 1.0 (HQ < 1.0), indicating no risk. Moreover, assessment of the long-term risk for ingestion of toxic metals indicated no risk (<10⁻⁶) based on the lifetime cancer risk (LCR). However, the LCR values of As and Cr were 5.3 × 10⁻⁶ and 2.5 × 10⁻⁶, respectively, demonstrating the most elevated LCR among the hazardous metals in terms of children’s exposure. Therefore, it is possible that children living in agricultural areas and participating in activities around the study area may be exposed to elevated concentrations of As and Cr.

The present study investigated the concentrations, sources, and potential health risk assessment of polycyclic aromatic hydrocarbons (PAHs) in house dust from residences in Samoeng District, Chiang Mai Province, Thailand. Samples of house dust from 48 households were analyzed for 16 PAHs. The total concentrations of PAHs (ΣPAHs) ranged between 270.1 to 45,386.8 ng g⁻¹, with a mean of 3942.4 ± 8175.1 ng g⁻¹. Pyrene (Pyr), benzo(k)fluoranthene (BkF), and indeno(1,2,3-cd)pyrene (IcdP) were the predominant compounds. Diagnostic ratios and principal component analysis (PCA) showed wood and the burning of biomass as the predominant sources. Evaluations of incremental lifetime cancer risk (ILCR) showed higher risks, especially for children (average ILCR = 6.57 × 10⁻³), with dermal contact as the main exposed pathway. Risks exceeded acceptable criteria (10⁻⁶ to 10⁻⁴), suggesting serious public health problems. The results highlight the significance of pollution mitigation measures, such as reducing the use of biomass combustion and improving indoor air quality, for protecting vulnerable populations in rural regions. The research conducted presents important insights into the environmental health impacts of PAHs in residences and shows the importance of public health procedures that can reduce exposure.

Chiang Mai (Thailand) experiences severe haze pollution in the dry season (December–April) each year mainly due to local and regional biomass burning (e.g. of agricultural land). A major component of the haze is airborne particulate matter (PM). During haze events, biomass burning is likely to be the dominant source of PM emissions, and at other times emissions from traffic dominate. The hazard of traffic derived PM has been extensively investigated previously but there are uncertainties regarding the toxicity of PM emitted from biomass burning. The toxicity of PM₁₀ samples collected during and after haze events in Chiang Mai in 2020 was compared in vitro in J774.1 macrophages as they are responsible for the clearance of inhaled particles. Diesel exhaust particles and ultrafine carbon black were included as benchmark particles as they have been commonly used as a surrogate for PM. Cytotoxicity was evaluated 24 h post exposure at concentrations of 3.9–125 µg ml⁻¹. Cytokine production (tumour necrosis factor alpha (TNF-α), interleukin (IL)-6, IL-1β, macrophage inflammatory protein (MIP-2)) was assessed and cell morphology visualised using light and scanning electron microscopy. The hydrodynamic diameter, zeta potential and endotoxin content of all particles was assessed as well as the metal content of PM samples. All particles induced a concentration dependent decrease in cell viability and increased TNF-α and MIP-2 production. Only PM samples stimulated IL-6 production and only non-haze PM caused IL-1β production. No change in IL-10 production was detected for any particle. PM samples and DEP caused vacuole formation in cells. The concentrations of endotoxin and metals were highest in non-haze PM, which may explain why it induced the greatest inflammatory response. As non-haze PM was more toxic than haze PM, our results indicate that the source of PM emissions can influence its toxic potency and more specifically, that PM emitted from biomass burning may be less toxic than PM emitted from traffic.

Indoor exposure to potentially toxic elements (PTEs) presents a global health concern, yet comprehensive seasonal assessments in Thailand remain limited, particularly during air pollution episodes. We assessed 15 PTEs in household dust collected across eight provinces of upper northern Thailand (UNT) during the haze and non-haze seasons to evaluate contamination levels, identify sources, and assess health risks. Five elements (Cr, Mo, Ni, Pb, and Zn) showed significantly higher concentrations during the haze season (p < 0.05), accompanied by corresponding increases in contamination indices and more diverse pollution sources being identified compared to the non-haze season, with Sb showing the highest enrichment degree (EF = 117.8). Source identification revealed potential enrichment from mixed anthropogenic sources, natural soil, industrial activities, agricultural inputs, and biomass burning. Health risk assessment showed that children faced unacceptable non-carcinogenic risks (HI = 2.51), increasing to 2.79 during the haze season, exceeding safe thresholds. Both adults and children experienced unacceptable carcinogenic risks from chromium exposure, particularly through inhalation during haze episodes. Total lifetime cancer risks increased from 1.20 × 10⁻⁴ to 1.74 × 10⁻⁴ for children and from 4.02 × 10⁻⁴ to 6.06 × 10⁻⁴ for adults during the haze season. These findings underscore the critical need for integrated pollution control strategies addressing biomass burning emissions to reduce indoor dust contamination and protect public health in biomass-burning-impacted regions.