Car pollution soars in Christchurch —but cause remains a mystery

Press, 4 July 1978, Page 1

Car pollution soars in Christchurch —but cause remains a mystery

By

DENISE McNABB

Christchurch traffic engineers, scientists, and doctors are mystified by the rising level in Christchurch of nitrogen oxide — a pollutant that usually conies from car exhausts.

The level of nitrogen oxide in Christchurch is increasing at a faster rate than is the number of vehicles through the city. Authorities on pollution attribute some of the increases to the slowing of traffic flows because of traffic lights and congestion. Cars idling, or accelerating then decelerating at slow speeds, give off more polluting gases than those travelling at more normal speeds. According to figures given by the Health Department's air pollution centre in Christchurch, nitrogen oxide levels exceeding the high level of 200 micrograms per cubic metre of air have increased markedly in the last four years. Yet traffic flows have not altered. An example is the stretch of Manchester Street between Hereford Street and Worcester Street. The department’s monitor recorded readings exceeding the high level in 1974 three times; in 1975, 14 times; in 1976, 34 times; and last year 41 times.

Miss Rosemary Patterson, assistant air pollution control officer, attributed some of the increase to the installation of traffic lights at Hereford Street and Worcester Street, causing acceleration and deceleration of vehicles. The City Engineer (Mr M. J. Gadd) said that the

lights were controlled by computers to stop traffic congestion. Mr Gadd agreed that the acceleration and deceleration of cars for traffic lights did increase nitrogen oxide, but he said that the rate of pollution increase could not all be attributed to traffic lights. The fact that the big increase of nitrogen oxides in Christchurch’s inner city cannot all be attributed to the lights and the traffic leaves a mystery. Perhaps in a time of recession, untuned cars are emitting more pollutants. A tune-up for a fourcylinder car is likely to cost about S3O. Mr Austin Cole, manager of Lichfield Motors, said that people definitely were leaving it longer before they had their cars tuned. Mr Cole said that cars

coming to his garage for tuning needed far more work done on them than in the past. He . estimated that if legislation enforcing emission tests came into being, 78 per cent of cars in Christchurch would fail. Miss Paterson said that the highest pollution level

year for Manchester Street was 711 micrograms of nitrogen oxide per cubic metre of air. That record for Christchurch was taken on June 17, and the average for the city that day was 505 micrograms. The Canadian air quality objectives say that maximum nitrogen oxide levels for 24 hours must not exceed 200 micrograms, and that the maximum tolerable level is 300 micrograms. Miss Paterson said that although the term “tolerable” was not explained by the Canadian authorities, sufferers from asthma and bronchitis would certainly not be able to tolerate levels above 300 micrograms.

Dr J. E. Ferguson, a reader in chemistry at the University of Canterbury, said that he was not sure

why the level of nitrogen oxides in Christchurch should be increasing to such an extent while the traffic flow remained stable, but a survey in Sydney had shown that slower speeds in town did increase the levels. Dr Fergusson said that the petrol quality in New Zealand had not changed in the last few years, and he did not think that the petrol grading now would lead to greater pollution. Dr M. McEwan, a lecturer in chemistry at the university, suggested that the temperatures at the time of the recordings should be noted, as there might be a link between the two. Dr J. McLeod, a chest physician at The Princess Margaret Hospital, said that the levels in Christchurch at present would certainly affect such people as asthmatics who already had damaged lungs, and those with sensitive noses and throats. Healthy people would be affected if the level of nitrogen oxide continually exceeded 200 micrograms for most of the year, Dr McLeod said. Smoke levels in Christchurch have exceeded the World Health Organisation’s goal of 120 micrograms per cubic metre of air, 10 times this year. The excessive smoke was recorded in May and June, and on the two days of this month. It was expected to be excessive again last evening. Lack of winds caused by a ridge of high pressure resulted in low-lying smog over much of Christchurch yesterday. Although the pollution appeared thick in parts the Meteorological Office described the temperature inversion layer as slight and the pollution as only moderate.

The office expected the inversion layer and absence of winds to continue today and possibly tomorrow.