Lai See | Beijing does not have the most polluted air in the world

For those of you familiar with Beijing's horrendous air pollution, it may come as a surprise to know that it is by no means the world's worst. That distinction went to Delhi. Indeed 13 of the top 20 cities in the world with the dirtiest air were to be found in India, three in Pakistan, and one in Iran, Qatar, Turkey, and Bangladesh. These findings were the result of a study, announced last week, of air quality in 1,600 cities by the World Health Organisation. The ranking is on the basis of annual average concentrations of PM2.5 particulates, which in Delhi were 153 micrograms (mg) per cubic metre.

The WHO says no PM2.5 levels are safe, though it regards annual average concentration of 10mg per cubic metre as a long-term guideline level beyond which people begin to suffer ill-effects. Beijing is ranked 77th with PM2.5 levels of 56, though this data appears to be old since the Beijing authorities said last month that PM2.5 particulates recorded a daily average of 89.5 mg per cubic metre in 2013. This would put Beijing 17th on the WHO rankings. Hong Kong is ranked 584th with PM2.5 levels of 21mg per cubic metre, though no year is given. This seems on the low side. Central, for example, averaged about 35 mg per cubic metre last year, which would put it at 288 on the list.

Following Delhi, the next ranked cities with the dirtiest air were Patna, Gwalior and Raipur, followed by Karachi. Singapore was ranked 755th with PM2.5 levels in 2011 of 17mg per cubic metre.

London was ranked at 836 with 16 mg per cubic metre and New York at 925 with 14mg per cubic metre. Sydney and Melbourne, with PM2.5 levels of 5mg per cubic metre, had the lowest for any sizeable cities.

Once again Australia is overall the most expensive major economy while the US is generally the cheapest, according to Deutsche Bank's third edition of its annual survey of global prices. The survey shows that Brazil is relatively expensive for a developing economy and while China is cheap for car rentals, for branded goods like Levi's jeans, Adidas shoes and iPhones it is more expensive than the US. Singapore was the most expensive place to buy a car, while Hong Kong the most expensive to rent an office.