Go to National Library of New Zealand Te Puna Mātauranga o Aotearoa
Volume 86, 1959
– 11 –

Report of Conservation Committee to The Royal Society of New Zealand on The Use and Effects of Modern Insecticides.

This matter was referred to the Royal Society in the first place following a request from the Entomological Society of New Zealand. This arose from an occurrence in Canterbury in which a large number of bees were killed following the aerial spraying of crops. The Committee has investigated this aspect of what might be thought to be the indiscriminate use of insecticides, particularly from the air, and has come to the conclusion that although in the early application of insecticides in this way in New Zealand some unexpected damage to bees did result, this problem has now been taken in hand by the Departments of Agriculture, Civil Aviation and Scientific and Industrial Research. As a result of deliberations between these Departments and the operators of aircraft, a suitable arrangement has been arrived at voluntarily which is now on trial, and which it is hoped will prevent recurrences of events such as occurred in Canterbury in 1955.

During its investigations the Committee enquired and sought statistical information from the D.S.I.R., the Director-General of Agriculture, the Director-General of Forestry, Director of the Cawthron Institute, Forest and Bird Protection Society, Royal N.Z. Institute of Horticulture, the British Medical Association and the Health Department, all of whom co-operated in supplying information. From the sifting of this information it would appear now that considerable danger can arise from the use of, more particularly, the chlorinated hydrocarbon type of insecticides to both stock and human beings. These dangers arise from—

(a)

Uninformed use of these substances by unskilled operators such as private individuals who have never handled them before;

(b)

Lack of precautionary measures of skilled operators:

(c)

Residues left on or in plants or in the soil.

(a)

Uninformed Use by Unskilled Operators.

(1)

The Health Department reports the case of a man who stirred a solution of parathion with his bare arm resulting in local burns on the forearm but, fortunately no serious aftereffects.

(2)

Several cases have been reported in the daily papers in some of which children have died, and also some adults, as a result of careless preparation of mixtures using organophosphates. Several people, both adults and children, have also died through using as drinking utensils, bottles which have contained parathion or hexone mixtures. In one case a child died after drinking water from a bottle which had contained hexone 12 months earlier.

(b)

Lack of Precautionary Measures

(1)

Numerous ailments and peculiar physiological conditions are reported as a result of both skilled and unskilled operators not taking adequate precautions when using organophosphates. Such cases are reported after the use of DDT, benzene hexachloride parathion and also after using chloropierin, mercury compounds and hormone weed killers. Most of these cases result from the inhalation of vapours, the accidental splashing on to the exposed parts of the body or into the eyes of these substances, and through being drenched by spray when spraying under windy conditions. In the case of chloropierin, two cases are recorded, one of a man

– 12 –

and one of a child dying due to exposure to chloropierin fumes. Other cases of illness and death are recorded following the use of bottles and jars which have contained parathion being used for storing of food-stuffs.

(2)

Out of these cases arises the question as to whether containers containing organophosphates and other powerful insecticides are being properly and adequately labelled. It appears to the Committee that all of these substances can be freely bought by any person. There is no system of control, compulsory registration or certification of any of these substances which would allow of control and labelling, or of the compulsory inclusion on the laber of information about suitable antidotes. There is in existence, however, a voluntary scheme for the certification of these products, but it is merely allowing for the preparation of a certificate stating that the preparation will carry out what is claimed for it, and this certificate is issued after field tests carried out, presumably by the D.S.I.R.

(c)

Residues

(1)

Practically nothing is known of the break-down products of chlorinated hydrocarbons or organophosphates used as insecticides, nor what these products are, either after application to the soil or to plants, little appearing in the literature in New Zealand or overseas. It is known that some micro-organisms are adversely affected by several of these compounds. Some 500 tons of pure DDT is being applied to agricultural land annually in New Zealand for the control of grass grub and subterranean caterpillar, and as this appears to have little effect on the productivity of the soil it is assumed that DDT has little if any effect on the micro-organisms in the soil.

(2)

Little is known of the recovery of chlorinated hydrocarbons from the soil, but some work which has been performed overseas would indicate that up to 80% of DDT can be recovered from the soil unchanged after two years.

(3)

Some work has been done in New Zealand and the results published, of the effect of the treatment of dairyland with DDT and benzene hexachloride, on the flavour of milk, cream and butter produce, from such treated lands. It has been found that milk, cream and butter can be tainted by the use of certain of these substances, in the matter of a few days.

(4)

Likewise, very little is known of the mode of action of these materials. In addition to the chlorinated hydrocarbons and organophosphate insecticides, there are now new materials appearing which do not fall into either of these two groups. Certain of the assumptions which have been made about these materials have recently been shown to be erroneous, for instance work on the inhibition of cholinesterase. Up till 1956 it had been assumed that certain types of these compounds operated in the same way in the inhibition of cholinesterase in animals. Recent discovery has shown that present theories relating to the mode of action of the thiophosphoryl insecticides are no longer tenable. Very little is known of the effect of any of these compounds in the animal system over long periods, for instance whether traces ingested can be excreted or whether they will gradually build up to a dangerous level of toxicity.

(5)

The use of systemic insecticides such as Metasystex is increasing. These substances are absorbed directly into the plant system and circulate in the transport system of the plant, so that any sucking insect is killed by the systemic insecticide.

(6)

Very little is known of either the duration of circulation of these systemic substances or of their break-down products, or their effect upon humans or other animals consuming the plants so treated.

(7)

New substances are continually coming on to the market for use as insecticides sometimes with extravagant claims made for them by their manufacturers and suppliers. In the opinion of the Committee, it is imperative, taking a long-term view, that the public should be protected from any adverse effects which these substances may be able to produce in either plants or animals for human consumption, or in plants offered for animal consumption.

The Committee therefore recommends that the Royal Society should draw the attention of the necessary authorities to these matters, and that—

(1)

A system of compulsory registration for all insecticides should be instituted in New Zealand through which control may be exercised where necessary.

(2)

That an active campaign be undertaken through the press and radio to educate the public in the use of and the precautions necessary to the safe handling of these substances.

(3)

That research be actively pursued into the type of residues produced in the soil and in plants by the continued use of all these substances.

(4)

That investigations be instigated immediately and pursued over a long period to ascertain the effect of continued ingestion of traces of these substances or their residues by both animals and the human population.

(5)

That all these substances be adequately labelled with particulars of antidotes, and that in the case of certain substances, if deemed necessary it be made compulsory to supply antidotes with the substance when purchased.

It is considered that these recommendations for investigation into the use of insecticides should also apply to the use of certain organic weed killers which are coming into widespread use.

J. T. Salmon,


October 24, 1957.
Convener Conservation Committee.