EESA10 - Assignment #1.pdf

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14 Apr 2012
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•Risk-Benefit Assessment Board
•Asbestos is a mineral with many unique properties, which aids in its many applications. Asbestos is able
to withstand high temperatures, chemical attack, wear, and as a poor conductor, acts as a very good
insulator against heat and electricity (Pintos, Parent, Case, Rousseau & Siemiatycki, 2009). Asbestos has a
wide variety of applications, but until the 1980s, it was mainly used in office buildings, public buildings
and schools as insulator against fire and sound (CHMC, n.d.).
Although asbestos has many practical applications, I disapprove of its widespread use. Studies have shown
that inhalation of asbestos fibers can cause health complications, such as: asbestosis, which describes severe
scarring of lung tissue that impairs lung function (CMHC, n.d.); and mesothelioma, a form of cancer which
affects the membranes lining internal organs (Pintos et al., 2009). Fiberglass can be used as a safe substitute
for asbestos insulation because it saves energy, money, and keeps a moderately temperate home across various
temperatures (Dodson, Hammar & Poye, 2008).
•DDT was widely used as a potent insecticide for agricultural and health purposes from the 1940s to 1970s,
until health concerns led to its prohibited use in most parts of the world (Eskenazi, Chevrier, & Rosas,
2009). DDT proved to be a cheap and effective means of vector control against mosquitoes and lice
helping to prevent malaria and typhus respectively.
I disapprove of the widespread use of DDT due to its toxic effects, its environmental persistence, and
concentration in the food supply. Due to its chemical stability, DDT tends to accumulate within the crops that
are sprayed, and people that consumed the crops became negatively affected by the chemical as is suggested by
current research in the field. A growing body of evidence presents that exposure to DDT may be associated
with adverse health outcomes such as breast cancer, diabetes, decreased semen quality, spontaneous abortion,
and impaired neurodevelopment in children (Eskenazi et al, 2009). Although DDT was very effective in
controlling the vector population, many species of insects are developing resistance to DDT, decreasing its
effectiveness as an insectide (C. F. Curtis and J. D. Lines, 2000). More research is required to find alternative
methods of vector control, as a substitute for DDT use in countries that are at high risk for malarial infections.
Chlorine is used as a disinfectant to purify drinking water, by eliminating harmful microorganisms.
Chlorination of drinking water is more beneficial than the use of alternative treatments because of the lower
health risks and its ability to degrade pesticides very effectively (Magara, Aizawa, Matumoto and Souna,
1994). Studies have shown that organic matter in the water and the amount of chlorine used to purify the
water can create harmful by-products (Cancer Research Society, 2010) However, by keeping the organic
matter and the chlorine at a minimum level, while ensuring the safe quality of the tap water, can help avoid
harmful by-products. I approve the widespread use of chlorine in tap water because it does not
exceptionally affect the human health and is a superior disinfectant compared to other disinfecting agents.
•a) Torontos only water source is Lake Ontario, which supplies drinking water to all residential and
commercial areas (City of Toronto, n.d.)
b) According to the City of Toronto’s website, these are the steps taken to ensure clean and safe drinking water is
provided to residents of Toronto. First, water intake pipes collect raw water from Lake Ontario, which then goes
through a screening process. The screening process removes large objects and debris. Chlorine and aluminum are
then added to kill any microorganisms and clump together any remaining small particles. ‘Flocs’ are formed from
the mechanical mixture of the two chemicals. Water then travels to the basin, where safe levels of chlorine are
added to kill any remaining microorganisms. After this stage, sulphur dioxide is added at the storage stage to
remove any excess chlorine. Fluoride is also added to prevent any cavities from forming. After adding chlorine,
sulphur dioxide, and fluoride, the water is sent through a filtration process where bits of floc, algae, silt, chemicals,
and impurities are removed. In a settling tank, heavy flocs drop out of the water to the bottom, and the cleaner
water is left at the surface. Before being distributed, ammonia is added to water to stabilize any remaining chlorine
and to keep the water safe during the trip from the plant to outside. Finally, the water is tested to ensure quality and
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