Methyl methacrylate and respiratory sensitization: A Critical review

Methyl methacrylate (MMA) is a respiratory irritant and dermal sensitizer that has been associated with occupational asthma in a small number of case reports. Those reports have raised concern that it might be a respiratory sensitizer. To better understand that possibility, we reviewed the in silico, in chemico, in vitro, and in vivo toxicology literature, and also epidemiologic and occupational medicine reports related to the respiratory effects of MMA. Numerous in silico and in chemico studies indicate that MMA is unlikely to be a respiratory sensitizer. The few in vitro studies suggest that MMA has generally weak effects. In vivo studies have documented contact skin sensitization, nonspecific cytotoxicity, and weakly positive responses on local lymph node assay; guinea pig and mouse inhalation sensitization tests have not been performed. Cohort and cross-sectional worker studies reported irritation of eyes, nose, and upper respiratory tract associated with short-term peaks exposures, but little evidence for respiratory sensitization or asthma. Nineteen case reports described asthma, laryngitis, or hypersensitivity pneumonitis in MMA-exposed workers; however, exposures were either not well described or involved mixtures containing more reactive respiratory sensitizers and irritants.The weight of evidence, both experimental and observational, argues that MMA is not a respiratory sensitizer

In Silico Investigation of the Thyroid Hormone Activity of Hydroxylated Polybrominated Diphenyl Ethers

Polybrominated diphenyl ethers (PBDEs) have been shown to have a disruptive effect on the thyroid hormone system, and one possible mechanism is the direct binding of their hydroxylated metabolites (HO-PBDEs) to thyroid hormone receptors (TRs). However, the experimental data on the thyroid hormone activity of HO-PBDEs are limited, and the molecular interaction mechanism remains unclear, impeding the ecological risk assessment for these widespread contaminants. In the present research, a quantum chemical approach was developed to predict the thyroid hormone activity of HO-PBDEs using the electronic structure parameters of neutral molecules. The ab initio HF/6-31G** algorithm was employed to optimize the molecular geometry and to calculate local molecular parameters regarding effective energy and electron transfer amount. The mechanistic analysis shows that the ability of the hydroxyl oxygen and hydrogen atom to donate or accept additional electron charges is an important property affecting the chemical activity of the thyroid hormone. The derived regression model was shown to have a good statistical performance and could be used to predict the thyroid hormone activity of other HO-PBDE congeners for which experimental measurements are not possible or are restricted. Therefore, the model has the potential to be a useful tool in the application of integrated testing strategies