Human Health Risk Assessment For Arsenic: A Critical Review

Millions of people are exposed to arsenic resulting in a range of health implications.This paper provides an up-to-date review of the different sources of arsenic (water, soil and food), indicators of human exposure (biomarker assessment of hair, nail, urine and blood), epidemiological and toxicological studies on carcinogenic and non-carcinogenic health outcomes, and risk assessment approaches. The review demonstrates a need for more work evaluating the risks of different arsenic species such as; arsenate, arsenite monomethylarsonic acid, monomethylarsonous acid, dimethylarsinic acid and dimethylarsinous acid as well as a need to better integrate the different exposure sources in risk assessments

Functional relation of ash-content with bulk density of coals

There coal samples with different ash-contents producing explosions under standard condition of temperature and pressure of Godbert’s apparatus were chosen for the study. The ash-contents and the bulk densities of each of the different range of particle-sizes were determined. The results obtained reveal that the bulk density increase with the increase of the ahs –content of all the three samples. The three empirical equations derived for each of the samples may be employed to evaluate the value of bulk density of any of them at any arbitrary value of the ash-content lying within the range of observation. The nature of variation of one parameter with respect to the other for all the three samples can be examined from the graphs

Functional relation of particle-size and bulk density along with indication of the latter's dependence on lump density

Four coal samples having different lump densities were sorted out and from each one of them ten ranges of particle-size and the corresponding bulk densities of each of them were determined. Empirical relations involving the bulk densities and the particle-size in microns have been developed for all the four samples. Fraction-wise variation of lump densities with bulk densities is also shown. The study not only affords to determine the load withdrawn from or produced per unit area and the volume required for a given mass of pulverized coal for its transportation and storage but also to provide a detailed picture of the fluctuation of lump densities with bulk densities of various particle-size-ranges usually encountered in problems of dust-air ignition

Experiments with metallic water troughs in a 300 ft. (91.5m) long surface steel gallery

Experiments conducted with metallic water troughs in the coal dust explosion suface steel gallery reveal that water troughs are quite effective in arresting the spread of flame beyond the zone of the barrier. It is also found that when the troughs are free to be dislodged from the position of rest, flame extinction is more effective than the situation when the water troughs are fixed to the body of the gallery. The flame is found to move with an accelerated velocity and the distance of the quenching zone from the position of the barrier is dependent on the concentration of water present. There is an optimum concentration of water to be present in the barrier for preventing the propagation of explosion