OCCUPATIONAL HYGIENE AND TOXICOLOGY

Occupational hygiene and toxicology



Occupational hygiene and toxicology

1 a)

The respirable silica dust enters the lungs and causes the formation of scar tissue, thus reducing the lungs' ability to take in oxygen. There is no cure for silicosis. Since silicosis affects lung function, it makes one more susceptible to lung infections like tuberculosis. In addition, smoking causes lung damage and adds to the damage caused by breathing silica dust.

Exposure occurs during many different construction activities. The most severe exposures generally occur during abrasive blasting with sand to remove paint and rust from bridges, tanks, concrete structures, and other surfaces. Other construction activities that may result in severe exposure include: jack hammering, rock/well drilling, concrete mixing, concrete drilling, brick and concrete block cutting and sawing, tuck pointing, tunneling operations.[1]

Other exposures to silica dust occur in cement and brick manufacturing, asphalt pavement manufacturing, china and ceramic manufacturing and the tool and die, steel and foundry industries. Crystalline silica is used in manufacturing, household abrasives, adhesives, paints, soaps, and glass. Additionally, crystalline silica exposures occur in the maintenance, repair and replacement of refractory brick furnace linings.

1 b)

Fiberglass batt insulation is still the preferred choice for residential construction. It is not necessarily the best type of insulation around and it is virtually not used in commercial and industrial construction. Fiberglass batt insulation used to come with a paper vapour barrier attached to one side. It would fit between the joists and had a reinforced paper edge for stapling the batts in place. [2]Today the standard fiberglass batts are slightly wider than the space between the wall studs or ceiling joists and are installed by friction-fit. Instead of each batt having its own vapour barrier, the barrier is now installed in wide sheets covering the insulation as well as the studs or ceiling joists. Batts are pre-cut to fit lumber spaced at 16" or 24" centers. Fiberglass insulation is also available in continuous rolls of up to 25 feet (7.6 m ) in length.Compressing the insulation reduces its effectiveness. Cutting it to accommodate electrical boxes and other obstructions allows air a free path to cross through the wall cavity. To prevent this from happening all outlet boxes have to be wrapped with a vapour barrier before installation. The airtight R-2000 outlet box is more effective, see vapour barriers.[3]

Also, gaps between batts can become sites of air infiltration or condensation (both of which reduce the effectiveness of the insulation) and requires strict attention during the installation. [4]

Fiberglass batts can be installed in two layers across an unfinished attic floor, perpendicular to each other, for increased effectiveness at preventing heat escaping. Batts can also be used to insulate a floor above an unheated crawl space. This can be a very unpleasant task and I speak from experience. Some years ago, I helped my son to re-insulate the floor underneath his home. Laying on our backs we first removed the old insulation. Next we added 2"x3"s to the 2"x6" floor joists and stapled a ...