In order to curb the outbreak of cholera stemming from a contaminated water pump, John Snow used the chemical chlorine to disinfect the water. This caused a dramatic decrease in cholera related deaths. The success was so profound that this method soon spread to the states.
The first state to adopt the chlorination method was New Jersey. It was introduced into the municipal water supply. Again, because of its effectiveness, the chemical then made its way over the past 100 years into 98% of all municipal water treatment facilities. In combination with sand filters, chlorination has all but eliminated cholera, typhoid, and dysentery from water supplies.
Chlorination is regarded as one of the most important health advancements of the past 1000 years.
In the United States alone, hundreds of millions of people receive chlorinated water through their taps.
That said, recent studies have made links between chlorine and asthma, among other ailments. Chlorine is poisonous to the human body, and though its effects are notably less than the contaminants which it eliminates, it also has adverse effects on health.
Additional home water filtering systems can help offset the chemicals included in tap water. Though vast health improvements have been made, there is always room for more improvements. A home water filtering system does the trick.