Viet Nam has an increasing need for building materials, including refractory bricks. Little is known regarding the occupational hazards incurred in brick manufacturing. To determine the occupational health hazards posed by a refractory brick operation in Ha Noi, Viet Nam, a cross-sectional occupational risk survey was conducted, focusing on respirable dust hazards. It included an industrial hygiene walk-through and gravimetric dust analysis. Noise, heat, lack of head protection, and dust exposure were hazards identified at the brick-manufacturing site. Respiratory protection involved a three-layer cloth mask that had not been tested for efficacy. Silica dust exposure levels exceeded the Vietnamese permissible exposure level by almost fivefold based on gravimetric assessment and estimated silica content. This brick manufacturing site contains significant injury and respiratory illness hazards. Further investigations are necessary to begin to develop occupational safety measures at the site.

In this thesis, we present the model of right-handed neutrinos at electroweak scale (EW⌫ R) and its extended version under two crucial tests by the electroweak precision measurements and the discovery of the 125 GeV SM-like Higgs boson. The key feature of the model is the existence of non-sterile electroweak scale right-handed neutrinos together with scalar triplets. We show that the EW⌫ R model with the new particle content satisfies well the constraint of the electroweak precision measurements through the contribution to the oblique parameters, S, T, U. Moreover, the 125 GeV SM-like Higgs discovery necessitates extending the minimal EW⌫ R model by adding one more complex scalar doublet and imposing a new symmetry. We present two very distinct scenarios in which the 125 GeV Higgs boson candidate of the model behaves like and unlike the SM one. In both cases, the signal strength of the 125 GeV candidate satisfies the experimental results of the LHC. The phenomenology of the heavy spin-zero states is also taken into account.-i