Final answer:
Emily buying arsenic introduces a discussion on its historical and contemporary uses, health risks associated with poisoning, and the significance of dosage in toxicity. Large-scale arsenic contamination in drinking water, like in Bangladesh, exemplifies its potential impact on public health.
Step-by-step explanation:
When Emily buys arsenic, she is purchasing a substance historically notorious for its use in poisoning cases, as well as for other practical applications.
In the past, arsenic was commonly used in pesticides, herbicides, and as a wood preservative, but its use has decreased due to its toxicity.
The consumption or exposure to arsenic can lead to serious health risks, including arsenic poisoning, with symptoms ranging from acute gastrointestinal distress to long-term effects like skin changes and increased cancer risks.
Drinking water contamination, as notably occurred in Bangladesh, is a critical issue where natural arsenic levels can lead to large-scale public health disasters.
The principle 'the dose makes the poison' is applicable, as while minimal amounts of certain substances may not be harmful, a higher dose, such as 0.5 g of arsenic, can be lethal.