Liver-Based Probabilistic Risk Assessment of Exposure to Organophosphate Esters via Dust Ingestion Using a Physiologically Based Toxicokinetic (PBTK) Model

Organophosphate esters (OPEs) are widely used and harmful to organisms and human health. Dust ingestion is an important exposure route for OPEs to humans. In this study, by integrating ToxCast high-throughput in vitro assays with in vitro to in vivo extrapolation (IVIVE) via physiologically based Toxicokinetic (PBTK) modeling, we assessed the hepatocyte-based health risk for humans around the world due to exposure to two typical OPEs (TPHP and TDCPP) through the dust ingestion exposure route. Results showed that the health guidance value of TPHP and TCDPP obtained in this study was lower than the value obtained through animal experiments. In addition, probabilistic risk assessment results indicate that populations worldwide are at low risk of exposure to TPHP and TDCPP through dust ingestion due to low estimated daily intakes (EDIs) which are much lower than the reference dose (RfDs) published by the US EPA, except in some regional cases. Most margin of exposure (MOE) ranges of TDCPP for children are less than 100, which indicates a moderately high risk. Researchers should be concerned about exposure to TDCPP in this area. The method proposed in this study is expected to be applied to the health risk assessment of other chemicals.

Organophosphate Esters in China: Fate, Occurrence, and Human Exposure

Organophosphate esters (OPEs) are widely used as flame retardants and plasticizers. OPEs have been released into various environments (e.g., water, sediments, dust and air, and soil). To investigate the occurrence and distribution of OPEs in various environments in China, this review collects and discusses the published scientific studies in this field. Chlorinated OPEs, as flame retardants, are the predominant OPEs found in the environment. The analysis of data revealed large concentration variations among microenvironments, including inflowing river water (range: 0.69–10.62 µgL−1), sediments (range: 0.0197–0.234 µg/g), dust (range: 8.706–34.872 µg/g), and open recycling sites’ soil (range: 0.122–2.1 µg/g). Moreover, OPEs can be detected in the air and biota. We highlight the overall view regarding environmental levels of OPEs in different matrices as a starting point to monitor trends for China. The levels of OPEs in the water, sediment, dust, and air of China are still low. However, dust samples from electronic waste workshop sites were more contaminated. Human activities, pesticides, electronics, furniture, paint, plastics and textiles, and wastewater plants are the dominant sources of OPEs. Human exposure routes to OPEs mainly include dermal contact, dust ingestion, inhalation, and dietary intake. The low level of ecological risk and risk to human health indicated a limited threat from OPEs. Furthermore, current challenges and perspectives for future studies are prospected. A criteria inventory of OPEs reflecting the levels of OPEs contamination association among different microenvironments, emerging OPEs, and potential impact of OPEs on human health, particularly for children are needed in China for better investigation.

A Review on the environmental and health impacts due to electronic waste disposal in Bangladesh

Bangladesh is one of the main importer countries of e-waste in the world. Moreover, country also generates e-waste about 2.81 million metric tons per year. However, majority of e-waste is being dumped into the open soil, open land, or open water bodies resulting problem on environment (i.e., pollution) and human population (i.e., health). Therefore, present review summarizes the environmental and health impact due to disposal of e-waste. Poorly management of e-waste during the collection, processing, recycling, and land filling causing environmental impact followed by air pollution, soil pollution, water pollution, and degradation of the beach because hazardous compounds spread to the surrounding or environment. Furthermore, e-waste also creates lots of health problems. Humans can be exposed to e-waste contaminants by the inhalation, dietary intake, dust ingestion, and dermic contact. In north eastern part of Bangladesh, about 36.3% women who lives near recycling sites experienced the death of a baby. Again, about 15% child laborers die, and 83% child laborers are affected by long term health problem because of e-waste mismanagement practice. There are about 120,000 Bhangaries who may be exposed to e-waste contaminants more seriously. The result of the study would provide us important insight into the growing concern of e-waste and would help policy maker for designing policy measure to recycle e-waste in a hazard free manner.

Dust Ingestion in a Rotorcraft Engine Compressor: Experimental and Numerical Study of the Fouling Rate

Helicopters often operate in dusty sites, ingesting huge amounts of contaminants during landing, take-off, hover-taxi, and ground operations. In specific locations, the downwash of the rotor may spread soil particles from the ground into the environment and, once ingested by the engine, may stick to the compressor airfoils. In the present work, the Allison 250 C18 engine’s multistage axial-flow compressor is employed to study the fouling rate on rotor blades and stator vanes from both numerical and experimental standpoints. The compressor is operated in a typical ground-idle operation, in terms of the rotational regime and contaminant concentration, in laboratory-controlled conditions. The mass of deposits is collected from the airfoil surfaces at the end of the test and compared to that estimated through the numerical model. The experimental test shows that the airfoils collect almost 1.6% of the engine’s total mass ingested during a ground-idle operation. The capability of numerical methods to predict the fouling rate on the rotating and stationary airfoils of a multistage compressor is tested through the implementation of literature based deposition models. Sticking models show a good agreement in terms of the relative results; nevertheless, an overestimation of the deposited mass predicted is observed.

Organophosphate Flame Retardants in Car Dust from Thailand and Implications for Human Exposure

Organophosphorus flame retardants (PFRs) are a group of compounds frequently detected in indoor dust that pose high health risks to exposure subjects. The present study reports on the investigation of the levels and profiles of seven target PFRs in car dust samples from Thailand. The samples were collected from the discarded air conditioning (AC) filter of 14 private cars (called AC dust samples) and from the bag filter installed in vacuum cleaners of 10 car washing services (called settled dust samples) in 2019. The concentrations of 7PFRs in AC dust samples were approximately 3,800-91,000 ng/g, whereas those from settled dust samples were about 11,000 to 15,000 ng/g. Tris (2-butoxyethyl) phosphate (TBEP) was found to be the most prominent of PFRs detected in both types of car dust with the highest concentration of 39,000 ng/g for AC filter dust and 10,000 ng/g for settled dust. The main PFR contributors in both dust types were TBEP (80%, 75%), followed by Tris (2-ethylhexyl) phosphate (TEHP) (9%, 5%) and tris(1-chloro-2-propyl)phosphate (TCPP) (7%, 4%), respectively. Tris(2-chloroethyl)phosphate (TCEP) and tri cresyl phosphate (TCP) were not detected in both types of car dust and tris(1,3-dichloro-2-propyl) phosphate (TDCPP) was found only in settled dust samples. According to the results of exposure assessment to PFRs in car dust, the human exposures via ingestion for adults and toddlers ranged from 1.69×10-2 to 2.67 and 10.6 to 2,360 ng/kg/day. The human exposures via inhalation for adults and toddlers ranged from 3.27×10-4 to 5.17x10-2 and 2.58×10-1 to 40.9 ng/kg/day. The highest exposure among PFRs corresponded to TBEP for both adults and toddlers and the risk through ingestion was higher than inhalation intake. Toddlers were more exposed to PFR contaminants in comparison to adults. When comparing the estimated average daily intake (ADI) values with the reference doses (RfDs) for PFRs, it was found that exposure to PFRs in car cabins via inhalation and dust ingestion is unlikely to have adverse human health effects.

Performance Degradation Due to Fouling and Recovery After Washing in a Multistage Test Compressor

Land-based power units have to fulfill even more high levels of production and reliability. In harsh environments (desert and tropical installations, typically), the power unit ingests high amounts of dust that might deposit inside the compressor. In this paper, the analysis of a multistage compressor performance that operates under sandy and humid conditions has been assessed. The compressor units, which equips the Allison 250 C18 compressor, has been subjected to multiple runs under severe conditions of soil dust ingestion. The compressor has been operated according to subsequent runs, and at the end of each run, the performance curve was recorded; the performance losses, in terms of pressure ratio, have been measured during the operations. The characteristic curve of each run is representative of the level of contamination of the unit. Finally, the compressor has been washed, and the performance curve, in the recovered conditions, has been recorded. The results show the modification and the downward shift of the characteristic curves which lead to a gradual loss of the compressor performance. The curves realized after dust ingestion have been compared with the recovered curve after online washing. The measurement shows a promising recovery of the performances, even if the compressor flow path appears affected by localized deposits able to resist to the droplet removal action. Detailed photographic reports of the inlet guide vane (IGV) and the first compressor stages have been included in this analysis. After each run, the IGV, the rotor blade and stator vane of the first stage, and the hub and the shroud surfaces have been photographed. The pictures show the deposition patterns on the blades and the compressor surfaces. The comparison of the pictures of the internal surfaces, before and after the washing, highlights the parts that are more critical to clean and needy of attention during offline washing and overhaul.

Mercury poisoning of a 4-year-old child by indirect contact to a mercury-containing facial cream: A case report

We report the severe mercury poisoning of a 4-year-old child by a so far unknown route of exposure, namely, by skin-to-skin contact. The child was admitted to the hospital with episodic pain in his extremities, tachycardia, hypertension, increased sweating, behavioral changes and weight loss. Extensive examinations eventually revealed an acute mercury poisoning. The initial mercury levels were 19 µg/L in urine (reference level 0.4 µg/L) and 37 µg/L in blood (reference level 0.8 µg/L). A facial cream bought online, containing approximately 18% mercury, was identified as the primary source of intoxication. The symptoms improved after disposal of the cream and chelation therapy. Further analyses, home visits and interviews suggested that the child was accidently intoxicated by skin-to-skin contact with the mother, although other routes of exposure such as dust ingestion and surface-to-skin contact cannot be excluded. The mercury levels in urine and blood samples of the child and other family members as well as in domestic dust samples decreased considerably over time.

Organophosphate flame retardants and diesters in urine of e-waste dismantling workers: Associations with indoor dust and implications for urinary biomonitoring

Indoor dust ingestion is one of the main pathways for human exposure to organophosphate flame retardants (PFRs). The urinary concentrations of diesters (DAPs) are usually used as biomarkers to assess...