Found this helpful and interesting fact sheet on the net.
Kathmandu is known as:
capital of Nepal
City of Temples
Total Population: approx. 1 million
Median age of Marriage: male 22, female 20
Life Expectancy: male 58, female 57 Nepal is the only country in the world where the male has a higher life expectancy
Drinking Water Problem: Kathmandu has a never ending water shortage problem. Do not drink water straight from the tap as underground water pipes have high deadly metal arsenic contents. Boil water, filter using standard water-filter before use.
Pollution: Kathmandu is Nepal's most polluted city caused mainly by emissions from industries, vehicle fuel combustion, re-suspension of road dust and also due to inefficient waste management. The city's air is vulnerable due to its bowl-like topography preventing air particles being disbursed. "Some wear masks, and some don't, but if it feels right for you, wear it while walking in Kathmandu!"
And I know from traveling that I must use only boiled or bottled water to brush my teeth plus no singing in the shower - keep mouth firmly closed.
Photo Source: Wikimedia Commons
Fact Sheet Source: http://www.nepalvista.com/travel/ktm.html