David Crawford: We're breathing poison air

As New Zealanders we value our country's clean, pure image. Our distance from the rest of the world comes with the bonus of clear, blue skies and clean air. Or does it? In reality, New Zealand has a vehicle emissions problem, and it is affecting our health.

We have one of the highest rates of asthma in the world. While no one study has pinpointed the definitive cause of these high asthma rates, various reports point to New Zealand's propensity towards underheated homes, agricultural sprays, and wood and coal smoke from household fires.

But another cause is emerging - we are paying the price for our high vehicle ownership rates.

According to World Bank data, New Zealand has the highest per capita ownership of vehicles in the world: 3.2 million and increasing each day.

The average age of the cars is 12 years, and as any mechanic will tell you, the older they get the more emissions they are likely to kick out, particularly if they are not properly maintained.

A number of studies show that vehicle emissions make asthma much worse. In Germany, a report concluded there was a 60 per cent increase in the amount of wheezing in children in high-traffic areas. A British study found children admitted to hospital with an asthma diagnosis were significantly more likely to live in an area with high traffic flow.

A Dutch study of 4000 2-year-olds found a positive association between asthma and levels of exhaust pollutants. A United States study found that the closer to a highway children live, the worse their wheezing and the more they need to use medication.

And a New Zealand study found that most of the worst cases of asthma are clustered around our urban centres.

Asthma costs this country more than $800 million a year in medical costs, including direct costs such as pharmaceuticals, patient costs, and primary care services as well as indirect costs like days off work and early death. One in six New Zealanders has asthma.

So what's in vehicle emissions that makes it so much harder for some of us to breathe?

Look no further than tiny particles of solid matter or liquid suspended in gas called PM10. They are so small they bypass the natural pollution traps in the nose and throat and settle in bronchial pathways and lungs, exacerbating asthma and bronchitis.

Studies have linked these particulates to premature death, and vehicle exhaust fumes are a major culprit. Exhausts also emit nitrogen dioxide which studies have linked to asthma.

To help reduce New Zealand's vehicle emissions, the Government is working on a package of initiatives.

From January this year, revised diesel fuel specifications have been in place to reduce the sulphur content in diesel fuels to 50 parts per million, making New Zealand diesel cleaner and bringing it in line with international standards.

Vehicles entering the country are required to meet the original emissions standards to which they were manufactured.

The Ministry of Transport is also working toward removing the barriers to the introduction of renewable transport fuels - including ethanol petrol blends and bio-diesel.

The next step is the visible smoke test, due to come into force on October 27.

A car's exhaust, during its warrant or certificate of fitness, will be checked while idling and then again while being revved for five seconds. If it blows clearly visible smoke, (particulates, carbon dioxide, nitrogen dioxide, carbon monoxide, sulphur dioxide, ozone, benzene and hydrocarbons) it won't be allowed on the road until it's repaired.

The check will take only about a minute - and seems a small price to pay for cleaner, healthier air.

* David Crawford is the Ministry of Transport's environment group manager.