My sister, who lives in Los Angeles, e-mailed me recently, saying: 'Yesterday we drove to downtown LA to get a smog certificate. Here in California, all cars and their engine emissions need to be tested at a licensed smog testing facility.

'When we were living in New Zealand we didn't have to get a smog certificate, but here in California all cars need to get tested every two years.”

In this already very polluted world, I ask this as a New Zealander. What is being done about smog checking and testing of vehicles here in New Zealand?

J I Clark, Tauranga.