Monday, October 24, 2022

The Riversdale Road gas emergency, 1975


Detail from 1957 Whites Aviation image, showing the large glasshouses complex at 5-7 Riversdale Road. Today, this site is now housing.
National Library of New Zealand, WA-43771

Just before 11 pm on 19 January 1975, residents living near to a set of three large glasshouses on 5-7 Riversdale Road in Avondale began to smell the acrid stench of a gas that had wafted up unto the night air, but failed to dissipate. The gas started an emergency that only lasted a matter of hours, but which emergency services took with absolute seriousness and caution. The gas, chloropicrin, was deadly if breathed into the lungs at quantity – and since World War I had a nasty reputation.

Chloropicrin was discovered in 1848 by Scottish chemist John Stenhouse. Considering Stenhouse became known for his work in developing respirators, that he came up with the lung-damaging chloropicrin in the course of his work as well is something of an irony.

The gas unfortunately came into something of its own when its disabling properties when applied to human beings was recognised and used on the battlefields of the Western Front during the First World War. It was said in 1918 that “the inhalation of ten cubic centimetres of chloropicrin gas makes a man sicker than Neptune at his worst, or than any other known emetic.” (Manawatu Standard, 5 November 1918)

This “tear gas”, however, revealed a benefit to the agricultural sector in the mid 1940s, when experiments showed that it destroyed fungi, insects, and halted the wilting of tomatoes grown under glass. The DSIR carried out experiments at their Mt Albert research facilities in Auckland in the 1947, and these produced good results.

In 1950, the substance hit the New Zealand market as “larvacide,” but the local press did advise caution.

“A product called “larvacide,” now being marketed in New Zealand for use in both soil fumigation and rabbit destruction, consists wholly of the poisonous chemical liquid chloropicrin. Damage to the lungs is the most important and most serious effect of chloropicrin vapour, and it is this property which makes it poisonous and ultimately causes death if enough of the vapour is inhaled. The lung-injuring properties of chloropicrin vapour led to its use as a war gas during the First World War.

“Fumes from “larvacide” are considerably less poisonous than the gas given off when “cyanogas” comes into contact with water or moist air, but it should be handled with the same care as “cyanogas” and all other poisonous materials.”

Putaruru Press, 2 February 1950

Accidents, though, with any dangerous substance, will happen.

“Poisonous chloropicrin or larvicide gas filtering through the Owaka Football club pavilion on Saturday night quickly put an end to a social function when guests had to evacuate the building. Complaints of sore eyes began about 11.30 and some were forced to go outside. Then everyone was cleared from the hall. The gas, which is nearly odourless, caused sore eyes and later severe headaches among many of those present. “Larvicide gas was widely used in the district for rabbit control before rabbit boards took over, and many farmers still have supplies of the gas capsules on their properties. Constable I Blue was called. He recovered part of a capsule which had apparently been broken into a drain that led through a shower room, from where the gas spread into the main social hall. The function was a farewell one for five members of the Owaka Football Club who will leave on Wednesday for a tour of Australia with a South Otago colts team.”

The Press (Christchurch) 15 March 1966

Another incident took place in an area similar to Riversdale Road, where residences and horticultural land by the 1970s were increasingly becoming close neighbours.

“Occupants of some houses on the outskirts of Havelock North left their homes; last night when a pungent, gas drifted over their properties. Some residents awoke with streaming eyes and sore throats. The gas was chloropicrin, or tear gas, used by fruit growers to fumigate soil. Mr M Mitchell, a poultry farmer, said his production was down and his fowls were spluttering and coughing. He had awakened coughing, at 3 am. Mr Mitchell said some of his neighbours had left their homes. Mr P Hawley said the gas was used by fruitgrowers to kill root fungi. It was applied by a contractor. “Because of the calm night, the gas just hung in the air,” he said. “Usually the wind blows it away and there are no effects.”

The Press (Christchurch) 31 March 1973

The incident at Avondale in January 1975 led to the temporary relocation of 30 people from the area immediately affected, some still in pyjamas and dressing gowns, many taking shelter in the school hall at Avondale College for the rest of the night.

Riversdale Road was cordoned off, and emergency services soon identified that the source of the gas was the three large glasshouses at 5-7 Riversdale Road, leased by Peter H Hilford. He had spread chloropicrin on the soil inside the glasshouses on Sunday 19 January, just hours before the emergency began. The Deputy Medical Officer of Health, getting to the scene just after midnight on 20 January, ordered that firemen hose down the soil, stopping the leakage.

Near dawn, at 5 am, the emergency was declared over, and the residents began to make their way back to their homes. An early morning wind helped disperse the last of the fumes, but people were asked to stay well clear of the glasshouses.

Hilford had done nothing wrong. Under the regulations of the time, all he had to do was follow the instructions on the chemical packet. But the incident helped impress upon the Government that there needed to be stricter restrictions on the use of the chemical, and that included watching the weather for any conditions which could cause the gas to collect in a cloud closer to the ground. Warm, still conditions on the night of 19 January helped keep the gas low enough to affect the surrounding area.

Accidents involving the chemical, though, were relatively rare, even though in 1975 authorities counted around 240 glasshouses in the Auckland area, and the chemical was used on an annual basis inside them. Chloropicrin is still in use today, usually on soil that is then covered in plastic sheets to prevent leakage. Its use is heavily regulated, with a number of steps that need to be taken by registered users.

No one wants another nasty surprise from that particular First World War reminder.

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