Survival of bacteria in adverse circumstances is promoted by special cellular mechanisms to detoxify chemicals. The biology of these remarkable detoxifying mechanisms has some surprising consequences. One of these is that toxic chemicals permitted in organic farming are relevant to dangerous outbreaks of untreatable infections in today’s hospitals.
Plasmids that bear resistance traits (eg copper-resistance in multiple-drug resistant plasmids) are thus themselves infectious, and can move from one species of bacterium to another. They are really analogous to dangerous viruses, and plasmids in the soil can become hospital plasmids quite easily. Plasmids bearing multiple resistance traits are a major reason why many dangerous bacteria such as Staphylococcus aureus are resistant to most modern antibiotics, and why hospitals outbreaks of infections that are untreatable by any antibiotic currently available are such a terrifying modern reality. We now live in the post-antibiotic era.
Overuse of antibiotics is the main cause of this problem, and restricting the use of antibiotics when they are not vital to human welfare is a good place starting point.
The fact that copper is extremely broad spectrum in its toxicity, is highly persistent in the environment, has been around the environment for billions of years, and that mechanisms of copper risistance are widely spread among different organisms underlines the importance of taking the human welfare implications of copper resistance traits of bacteria seriously.
A recent scientific paper
“Copper amendment of agricultural soil selects for bacterial antibiotic resistance in the field” (J. Berg 1,2, A. Tom-Petersen 1,2 and O. Nybroe 1 Letters in Applied Microbiology 2005, 40, 146–151 765X.2004. (1Department of Ecology, Royal Veterinary and Agricultural University, Frederiksberg C, and 2Department of Microbiology, Danish Institute for Food and Veterinary Research, Copenhagen V, Denmark ))
provides strong evidence on why we should be concerned about agricultural use of copper based fungicides as definite activities that promote the spread of multiple-drug resistant bacteria. To quote the Berg 2005 papers’ main conclusion
“In Australia , copper-containing sprays of various formulations … have been used to control fungal diseases in pome and stone fruit orchards, vineyards and vegetable crops for well over 100 years (Merry et al. 1983). Over 7500 t yr-1 of Cu fungicides have been used, representing 13% of the global total (Lepp and Dickinson 1994). In stark comparison, England and Wales were estimated to use only 8 t of Cu fungicide between them in the year 2000 (Nicholson et al. 2003).
(Lukas Van-Zwieten, Graham Merrington and Melissa Van-Zwieten, 2004. SuperSoil 2004: 3rd Australian New Zealand Soils Conference, 5 – 9 December 2004, University of Sydney , Australia . website www.regional.org.au/au/asssi/)
“Horticultural and viticultural operations with a long history of copper fungicide application have resulted in accumulations of copper in surface horizons (Gallagher et al. 2001; Chaignon et al. 2003). Prolonged use in Europe has lead to high levels in the soil (200-500 mg/kg in France, Brun et al. 1998), which has affected a large portion of agricultural land. An Australian study found up to 250mg/kg total copper in a 20-30 yr old vineyard soil, while 8-14 vineyards studied exceeded 60 mg/kg (Pietrzak and McPhail 2004). Similarly, avocado orchard soils in northern NSW were recently observed to have even greater soil Cu residues (280-340 mg/kg) (Merrington et al. 2002).”
Organic farmers generally ban antibiotic use, but continue to tolerate use of copper based fungicides. In the GMO Pundit's opinion, if they are to continue to have credibility in providing the community with environmentally virtuous practices, they should be consistent, and ban copper fungicides.
There are good synthetic antifungal alternatives to copper but the organic movement declines to use them for no good reason.
For example Anthony Trewavas in
Trewavas, A. 2004. A critical assessment of organic farming-and-food assertions with particular respect to the UK and the potential environmental benefits of no-till agriculture. Crop Prot. 23:757–781.
has provided a critical comparison of mancozeb, a synthetic fungicide, with copper sulphate used by the organics movement.To quote him:
Table 1 makes some limited comparisons between mancozeb, a synthetic copper fungicide usually used to treat late blight, and the organic pesticide equivalent, copper sulphate. The full table can be found in Leake (1999a). In environmental qualities, mancozeb is superior in all categories compared to copper sulphate. In terms of human health, copper sulphate is corrosive and toxic and has caused liver disease in European vineyard workers. Although the EC theoretically banned copper sulphate in 2002, no alternative has been found for organic farmers and thus it continues to be used. The consequences of not using copper sulphate properly have been reported as organic farms acting as repositories of late blight, a serious disease of potato (Eltun, 1996; Zwankhuizein et al., 1998) or seriously damaged orchards (Van Embden and Peakall, 1996). Any sensible approach would determine use based on toxicity.
Leake, A., 1999a. House of Lords Select committee on the European communities. Session 1998–1999, 16th report. Organic farming and the European Union. HMSO, London, pp. 81–91.
Mancozeb does not contain copper: it contains zinc and manganese.
ReplyDeleteThat's even better for his argument too.
ReplyDelete