Lead hydrogen arsenate
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| General | |||||||||||||||||||
| Surname | Lead hydrogen arsenate | ||||||||||||||||||
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| Molecular formula | PbHAsO 4 | ||||||||||||||||||
| Brief description |
White dust |
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| properties | |||||||||||||||||||
| Molar mass | 347.15 g mol −1 | ||||||||||||||||||
| Physical state |
firmly |
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| density |
5.79 g cm −3 |
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| Melting point |
Decomposes on heating |
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| solubility |
heavy in water |
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| Authorization procedure under REACH |
particularly worrying : carcinogenic, toxic for reproduction ( CMR ) |
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| As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . | |||||||||||||||||||
Lead hydrogen arsenate , usually as lead arsenate called, was from the 1890s until the 1960s, a much used in agriculture pesticides . It was used in particular against the Colorado potato beetle , the codling moth and in viticulture . The regulations for handling this substance and its residues differed from country to country. In Germany, the use of lead arsenate in viticulture was banned as early as 1928, but in the USA it was the most widely used insecticide for half a century .
Composition and manufacture
In the beginning, lead arsenate had to be produced by the farmers themselves from soluble lead salts and sodium arsenate. Most commercially available was "acid" lead arsenate PbHAsO 4 , "basic" lead arsenate Pb 5 OH (AsO 4 ) 3 was used in certain regions of California.
history
use
For example, lead arsenate has been used in the United States, Australia, Canada, New Zealand, Japan, England, France, and North Africa. The most important use was the control of codling moth, but it was also used against insect pests in other fruit crops, on vegetables or ornamental lawns, in rubber and coffee plantations, for combating mosquitoes and in immersion baths for cattle.
United States
discovery
In the USA towards the end of the 19th century, the arsenic Parisian green was used against Colorado beetles . For the chemical control of the gypsy moth, Parisian green proved to be unsuitable, in tests in the 1890s lead arsenate showed a better effect against the gypsy moth. The first-time use of lead arsenate for insect control is credited to CH Fernald, an employee of the Division of Entomology at the US Department of Agriculture . Since lead arsenate stuck to the leaves longer and was better tolerated by plants than Parisian green , it also pushed it out of use in potato cultivation. In fruit growing, lead arsenate was used against codling moth .
Backlog problem
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By the early 1920s, the focus of American fruit growing had shifted from the rainy state of New York to the interior of Washington state . In the semi-arid climate there, the orchards had to be artificially irrigated; the rain could no longer wash the pesticide residues off the fruits. In addition, better binding agents have now been added to the lead arsenate, it stuck to the fruit better and reached the consumer.
In the fall of 1919, a Boston health inspector saw pears with a floury coating on a market cart. When it turned out to be lead arsenate, the Bureau of Chemistry , which was responsible for food control at the time, traced the origin of the fruit back to the west coast. It turned out that it was an isolated incident. Nonetheless, in the years that followed , the Bureau of Chemistry continued sampling and trying to convince farmers of the need to clean their fruit before selling it. Occasionally, a delivery of fruit was confiscated due to high arsenic content, but in no case were criminal charges filed or fines imposed. The level of the informal arsenic limit was only known to the Bureau staff . There was no advice to consumers to wash fruit before consumption, as there was fear of panic reactions and damage to the fruit industry.
In October 1925, two cases of arsenic poisoning in England were attributed to consumption of American apples. This caused great concern in England that the market for fruit imported from the USA was about to collapse. Investigations were initiated against several fruit importers, and the House of Commons dealt with the incident. The Bureau of Chemistry then developed a voluntary certification system to ensure that apple exports to the UK met the UK limit of 0.010 grains / pound (about 1.43 mg / kg) arsenic oxide . For this purpose, apples destined for export were washed in a washing facility specially built in the port of New York. State-licensed chemists, who were paid by the exporters, were commissioned with monitoring.
Limit values
Although the affair had hardly caused a stir in the USA, it would have been difficult to justify not introducing an arsenic limit value here. However, this met with stubborn resistance from fruit producers and their lobbyists . Their attempt to exclude fresh fruit and vegetables from the requirements of the Pure Food Act of 1906 failed in 1926 due to resistance from the House of Representatives .
The Ministry of Agriculture recommended that farmers wash their fruit after the harvest. At the same time, more samples were taken. If the arsenic levels were too high, the owners of the fruit deliveries were given the choice of cleaning their goods or having them destroyed; no penalties were imposed. In January 1927, a commission appointed for this purpose recommended tolerance values of 3 ppm or 0.021 grain / pound (gr./lb.) For arsenic and 2 ppm or 0.014 gr./lb. for lead. In February 1927 the Ministry of Agriculture only set a limit value for arsenic of 0.025 gr./lb. firmly. The Food and Drug Administration , which was founded in 1927 and into which the Bureau of Chemistry was absorbed, continued to lower this limit annually until the British limit was reached in 1932. A limit value for lead was not initially imposed because the determination of the lead content took about a day at that time, which is impracticably long for perishable goods. It was believed that washing off the arsenic would also remove the lead. It wasn't until 1932 that FDA chemists had developed a reliable rapid test for lead. In February 1933, Agriculture Secretary David F. Houston set the limit value for lead to 0.025 g / lb. firmly. In April, at the instigation of the Assistant Secretary of Agriculture, Rexford G. Tugwell , it was reduced to 0.014 g / lb. lowered. Due to violent protests by the International Apple Association , a lobby organization for apple growers , Agriculture Minister Henry A. Wallace raised the lead limit to 0.020 gr./lb again in June. on. The limit values for lead between 1935 and 1937 were 0.018 gr./lb. and in 1938 were again down to 0.025 g / lb. elevated.
Throughout this time, the FDA has been careful not to draw attention to the residue problem out of consideration for the fruit growers. In the early 1930s, some medical professionals published studies that underlined the dangers of the spray residues. However, as a result of the Great Depression , no measures could be implemented that would have increased the farmers' production costs.
The FDA began extensive laboratory studies on the long-term toxicity of arsenic and lead in 1935. The funds for this were no longer approved for the 1937 financial year. Instead, the US Public Health Service was hired to look for symptoms of acute poisoning in residents of Chelan County in Washington, where 20 to 25% of American apple production was then produced and 4.5 million pounds of lead arsenate was applied annually . No cases of acute lead or arsenic poisoning were found there within a three-year investigation period. On the basis of this study, the Farm Security Administration responsible at the time set the limit values for arsenic to 0.025 grain / pound (gr./lb.) And for lead to 0.050 g / lb. high.
Decrease in consumption
When, after 1946, DDT, a far less toxic and at the same time more effective insecticide, became available, the use of lead arsenate in fruit growing slowly declined. In the apple orchards in the north-west of the USA, the conversion was completed in 1948, because the codling moth population there had become resistant to arsenates. The last reports of the use of lead arsenate in American agriculture are from the mid-1960s. The EPA environmental protection agency issued a ban on use on August 1, 1988, but no lead arsenate preparation had been approved for a long time before.
| 1931 | 1935 | 1937 | 1953 | 1957 | 1959 |
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| 17,225 t | 23,650 t | 28,700 t | 7,650 t | 6,440 t | 5,400 t |
Switzerland
In Switzerland, the company Dr. Rudolf Maag AG offered a lead arsenate paste for use against codling moth and hayworm, the first generation of grape moth, from 1920 . Because of its high toxicity, lead arsenate first had to be sold through pharmacies. The health authorities refused to liberalize the sale of arsenic in 1924 because of its toxicity and lack of demand. Compared to the remedies common at the time, however, the control of the hayworm with lead arsenate would have been 25 times cheaper than with pyrethrum and 15 times cheaper than with nicotine . The interest representation of the fruit and wine growers therefore succeeded in drawing up a model ordinance on the traffic with toxic plant protection products . At a conference in April 1926, representatives of the agricultural associations, the research institutes and the pesticide manufacturers spoke out in favor of approval under the new ordinance, while the bird protection representative voted against it and a medical practitioner thought lead arsenate in particular was too risky. The cantons only implemented the model ordinance that was finally passed inconsistently. Limit values for arsenic residues on fruit have not been set in Switzerland. In the period that followed, the consumption of lead arsenate rose sharply, with Maag selling 67.3 tons in 1928. In western Switzerland it was mandatory from 1937 to treat the potato fields with lead arsenate as a precautionary measure because of the Colorado potato beetle advancing from France. Lead arsenate was only effective against the beetle larvae. At the beginning of the Second World War, the annual requirement for arable and viticulture was estimated at 158 tons per year. From 1940 on, the cheaper calcium arsenate was increasingly used against the Colorado beetle.
In 1936, 30 people in Oberstammheim (Canton Zurich) fell ill after eating bread mixed with lead arsenate. The background to the incident could not be clarified.
Germany
In Germany , experiments with arsenic preparations for fruit and wine growing were carried out from 1905 on. In 1906, the Royal Institute for Viticulture, Fruit Growing and Horticulture in Geisenheim asked the Imperial Health Department in Berlin about the approval of "arsenic acid lead", but this refused.
Arsenic was also listed in the first plant protection product directory of the Biological Reichsanstalt für Agriculture and Forestry , which appeared in 1920. Lead arsenate was initially used in fruit growing, where it was valued because of its good adhesion and plant compatibility, but also because of its ability to float (low tendency to settle) in the spray mixture. Before lead arsenate was approved in viticulture, the Reich Committee for Wine Research commissioned several studies to test its suitability in 1926. The high levels of lead residue were noticeable (wine 0.5 - 9 mg Pb / l, pomace 8 - 14 mg, black horse 106 mg, wine yeast 207 mg Pb / kg). The sub-committee for pest control of the German Viticulture Association therefore spoke in November 1927 for a ban on use instead of approval. As early as the spring of 1928, the Reich Ministry of Food and Agriculture ordered a ban on the use of lead-containing compounds and their preparations in viticulture. Lead arsenate appears to have been used in fruit growing in Germany until around 1960.
Austria
The poison ordinance of 1928 allowed the use of lead arsenate in viticulture , but it had to be done before flowering.
Individual evidence
- ↑ a b c d e f Entry on lead (II) hydrogen arsenate in the GESTIS substance database of the IFA , accessed on February 18, 2017(JavaScript required) .
- ↑ Entry on Lead hydrogen arsenate in the Classification and Labeling Inventory of the European Chemicals Agency (ECHA), accessed on February 1, 2016. Manufacturers or distributors can expand the harmonized classification and labeling .
- ↑ Entry in the SVHC list of the European Chemicals Agency , accessed on July 17, 2014.
- ↑ Swiss Accident Insurance Fund (Suva): Limit values - current MAK and BAT values , accessed on October 24, 2016.
- ↑ a b c d Francis J. Peryea: Historical use of lead arsenate insecticides, resulting soil contamination and implications for soil remediation ( Memento of December 7, 2008 in the Internet Archive ). Proceedings, 16th World Congress of Soil Science (CD Rom), Montpellier, France, 20. – 26. August 1998
- ↑ a b c Lukas Straumann: Useful pests . Chronos Verlag, Zurich, 2005, ISBN 3-0340-0695-0
- ↑ a b c d e Thomas R. Dunlap: DDT: Scientists, Citizens and Public Policy . Princeton University Press, 1981, ISBN 0-691-04680-8 .
- ↑ Ordinance implementing the ordinance on pest control with highly toxic substances . March 29, 1928, Reichsgesetzblatt Part I No. 16 of April 5, 1928
- ^ A b Paul Claus: Arsenic for pest control in viticulture 1904–1942 . Writings on wine history, No. 58, Wiesbaden 1981, ISSN 0302-0967