Phthalate concentrations in house dust, their associations with household characteristics, and spatial distribution across rural and urban areas in southern Thailand

Phthalates pose a significant health concern because they can leach from consumer products into the environment, leading to human exposure and potential adverse health effects. This cross-sectional study investigated phthalate concentrations in house dust collected from urban and rural areas in southern Thailand, examining their associations with household characteristics and spatial distribution across two communities. Two types of dust samples (multi-surface dust and floor dust) were collected from 310 houses using a vacuum cleaner before the monsoon season (March–April 2023). Ten phthalates were quantified using isotope-dilution gas chromatography–mass spectrometry. At least one phthalate was detected in all samples of house dust. DEHP, DnOP, and DBP were detected in 100%, 97.4%, and 88.7% of the samples, respectively, with DEHP showing the highest concentration (6528 μg/g). The geometric mean concentration of total phthalates (Σ10PAE) was 192 μg/g. Phthalate concentrations in the urban area houses (mostly located in commercial zones) were significantly higher than those in rural area houses (p < 0.005). According to the generalized linear models, phthalate concentrations were significantly associated with certain housing characteristics (e.g., household income, residential business operations, use of floor coverings) and indoor environmental factors (e.g., humidity and temperature). Households in close proximity to gas stations and vehicle repair shops appeared to have increased phthalate concentrations in dust. These findings are useful for Thailand and its local government in establishing appropriate guidelines to monitor phthalates in the environment and to reduce phthalate exposure via inhalation of contaminated household dust among Thai people.