Concentrations and human exposure to hexabromocyclododecane and tetrabromobisphenol A from the indoor environment in Bangkok metropolitan area, Thailand

Aim: This study investigated hexabromocyclododecane (HBCDD) and tetrabromobisphenol A (TBBPA) concentrations in indoor dust from houses, offices, and cars and estimated toddler and adult exposure to HBCDD and TBBPA through dust ingestion.Methods: The concentrations of HBCDD and TBBPA were measured in 47 indoor dust samples collected from the Bangkok metropolitan area, Thailand. All samples were analyzed for HBCDD and TBBPA using LC-MS/MS. The estimated daily intake (EDI) through dust ingestion was calculated from the median and 95th percentile concentrations of HBCDD and TBBPA.Results: HBCDD was detected in 47% of samples, and TBBPA was detected in all samples. The median concentrations of HBCDD were 6.7 ng g-1, <0.7 ng g-1, and <0.7 ng g-1 in cars, houses, and offices, respectively. The isomer composition of ∑HBCDD in dust was: α-HBCDD (40%-54%), γ-HBCDD (19%-40%), and β-HBCDD (17%-28%). In contrast, TBBPA was observed at higher concentrations, with median values of 674, 67, and 22 ng g-1 in offices, houses, and cars, respectively. Under a median exposure scenario, toddlers were exposed to 0.05 ng kg-1 bw day-1 for HBCDD and 0.25 ng kg-1 bw day-1 for TBBPA, with adults exposed to 0.01 and 0.06 ng kg-1 bw day-1 for HBCDD and TBBPA respectively.Conclusion: Concentrations of HBCDD in dust from Thai cars, homes, and offices are lower than those of TBBPA following the listing of HBCDD in the Stockholm Convention on Persistent Organic Pollutants and limited use of HBCDD in Thailand in applications such as building insulation foam. Concentrations of TBBPA in office dust significantly exceeded (P < 0.05) those in house and car dust owing to the greater number of electronic appliances and poor natural ventilation in offices. EDIs for Thai toddlers exceeded those of adults under both median and high-end exposure scenarios. However, EDIs of HBCDD and TBBPA for the general Thai population were below the corresponding oral reference dose guidelines

Concentrations of Tetrabromobisphenol-A and hexabromocyclododecane in Thai child daycare centre dust and the exposure risk for young children

Children spend one-third of their day in child daycare centres, where they may be exposed to toxic chemicals, such as tetrabromobisphenol-A (TBBPA) and hexabromocyclododecane (HBCDD), from indoor dust. However, studies on the exposure of TBBPA and HBCDD in schools remain scarce, especially in Thailand, where no such study has yet been reported. Therefore, in this study, we collected dust samples from 20 child daycare centres in Thailand and analysed them for flame retardants, TBBPA and HBCDD. TBBPA was detected in all samples with a median concentration of 35 ng g−1 (range, 14–5017.7 ng g−1). The median level of HBCDD was lower than the quantitation limit (LOQ) with <LOQ to 86.6 ng g−1 of dust sample. The electronic density score was calculated from the number of electronic appliances divided by each sampled surface floor area that revealed an abundance of TBBPA in the dust in rooms with many electronic items. The use of electronic devices, especially printers, that were found to be related to the high TBBPA concentration in the room, should be minimised in child daycare centres. The children's exposure to these chemicals from dust was estimated for dust ingestion and dermal absorption. The combined exposure was lower than the established reference dose value, and the hazard quotient for children via these two pathways were ranged 0.7 × 10−6 – 2.7 × 10−4 for TBBPA and 1.8 × 10−5 – 4.9 × 10−5 for HBCDD, which did not exceed 1.0. Although there is uncertainty regarding the potential health effects of long-term exposure to these substances, it is undeniable that child daycare centres represent a source of exposure to these substances for children. Further investigation of other intake routes of several flame retardants in child daycare centres and identification of the sources of these substances is warranted to decrease children's health risks from exposure to these harmful substances in child daycare centres

Electrochemical Sensor Based on a Composite of Reduced Graphene Oxide and Molecularly Imprinted Copolymer of Polyaniline–Poly(<i>o</i>‑phenylenediamine) for Ciprofloxacin Determination: Fabrication, Characterization, and Performance Evaluation

Contamination of antibiotics in water is a major cause of antibiotic resistance (ABR) in pathogens that endangers human health and food security worldwide. Ciprofloxacin (CIP) is a synthetic fluoroquinolone (FQ) antibiotic and is reportedly present in surface water at a concentration exceeding the ecotoxicological predicted no-effect concentration in some areas. This study fabricated a CIP sensor using an electropolymerized molecularly imprinted polymer (MIP) of polyaniline (PANI) and poly(o-phenylenediamine) (o-PDA) with CIP recognition sites. The MIP was coated on a reduced graphene oxide (rGO)-modified glassy carbon electrode (rGO/GCE) and operated under a differential pulse voltammetry (DPV) mode for CIP detection. The sensor exhibited an excellent response from 1.0 × 10–9 to 5.0 × 10–7 mol L–1 CIP, showing a sensor detection limit and sensitivity of 5.28 × 10–11 mol L–1 and 5.78 μA mol–1 L, respectively. The sensor’s sensitivity for CIP was 1.5 times higher than that of the other tested antibiotics, including enrofloxacin (ENR), ofloxacin (OFX), sulfamethoxazole (SMZ), and piperacillin sodium salt (PIP). The reproducibility and reusability of the sensor devices were also studied