The use of

DDT Dichlorodiphenyltrichloroethane, commonly known as DDT, is a colorless, tasteless, and almost odorless crystalline chemical compound, an organochloride. Originally developed as an insecticide, it became infamous for its environmental impacts. ...

New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...

was banned in 1989 due to negative environmental impacts.

DDT

DDT is an organochlorine insecticide that does not occur naturally. It is a

persistent organic pollutant Persistent organic pollutants (POPs), sometimes known as "forever chemicals", are organic compounds that are resistant to environmental degradation through chemical, biological, and photolytic processes. They are toxic chemicals that adversely ...

(POP) with a half life of 2–15 years. Concerns were raised about its use in the 1940s but the publication of Rachael Carson's book ''

Silent Spring ''Silent Spring'' is an environmental science book by Rachel Carson. Published on September 27, 1962, the book documented the environmental harm caused by the indiscriminate use of pesticides. Carson accused the chemical industry of spreading d ...

'' was the catalyst leading to DDT being banned. DDT was first banned in Hungary in 1968 then in Norway and Sweden in 1970, the US in 1972 and the United Kingdom in 1984.

Usage

DDT was used extensively for agricultural use in the 1950s and 1960s to control grass grub and porina moth. It was also used on lawns and for market gardens. Some 500

ton Ton is the name of any one of several units of measure. It has a long history and has acquired several meanings and uses. Mainly it describes units of weight. Confusion can arise because ''ton'' can mean * the long ton, which is 2,240 pounds ...

s was being applied annually by 1959. By the 1970s its use was restricted and was banned in 1989.

Residues

There was increasing evidence, especially in the 1970s, that there were DDT residues in aquatic organisms including trout and eels. Being

bioaccumulative Bioaccumulation is the gradual accumulation of substances, such as pesticides or other chemicals, in an organism. Bioaccumulation occurs when an organism absorbs a substance at a rate faster than that at which the substance is lost or eliminated ...

DDT passes up the food chain and organisms at higher

trophic level The trophic level of an organism is the position it occupies in a food web. A food chain is a succession of organisms that eat other organisms and may, in turn, be eaten themselves. The trophic level of an organism is the number of steps it i ...

s end up with high concentrations of the pesticide. Some Canterbury and Southland farms have elevated levels of DDT and a programme run by the Ministry of Agriculture ensures that exported meat and dairy produce have low levels of these residues. During dry periods animals ingest soil since grass is shorter and sparser and the DDT residue on the soil is retained by the animal. In the 1980s 40% of the lambs in Canterbury, a region with low rainfall and occasional droughts, had DDT levels that were above the

European Union The European Union (EU) is a supranational political and economic union of member states that are located primarily in Europe. The union has a total area of and an estimated total population of about 447million. The EU has often been des ...

's permitted limit but still acceptable under safe tolerance limits for New Zealand. Māpua was one of the most contaminated sites in New Zealand due to pesticide residues in the soils from a now defunct factory. In the 1940s

organomercury Organomercury refers to the group of organometallic compounds that contain mercury. Typically the Hg–C bond is stable toward air and moisture but sensitive to light. Important organomercury compounds are the methylmercury(II) cation, CH3Hg+; ...

and

organochlorine An organochloride, organochlorine compound, chlorocarbon, or chlorinated hydrocarbon is an organic compound containing at least one covalent bond, covalently bonded atom of chlorine. The chloroalkane class (alkanes with one or more hydrogens subst ...

pesticides, including

, DDD,

dieldrin Dieldrin is an organochloride originally produced in 1948 by J. Hyman & Co, Denver, as an insecticide. Dieldrin is closely related to aldrin, which reacts further to form dieldrin. Aldrin is not toxic to insects; it is oxidized in the insect to fo ...

, 2,4-D and

paraquat Paraquat (trivial name; ), or ''N'',''N''′-dimethyl-4,4′-bipyridinium dichloride (systematic name), also known as methyl viologen, is an organic compound with the chemical formula C6H7N)2l2. It is classified as a viologen, a family of redox ...

, were produced. The factory closed in 1988 and the site was subjected to a major cleanup operation in the 2000s. DDT has also been found in the endangered Hectors dolphin which inhabits the coastal regions on New Zealand.

Stockholm Convention

The New Zealand government has signed and ratified the

Stockholm Convention Stockholm Convention on Persistent Organic Pollutants is an international environmental treaty, signed on 22 May 2001 in Stockholm and effective from 17 May 2004, that aims to eliminate or restrict the production and use of persistent organic ...

which controls the production and use of persistent organic pesticides, and therefore includes DDT. It came into law on 23 December 2004. Article 3.1(b) of the Convention restricts the production and use of DDT but since there is no intention to use DDT in New Zealand there is no action required under the Convention.

References

{{Reflist, 2

Pesticides in New Zealand

DDT

Usage

Residues

Stockholm Convention

See also

References