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== Exposure ==
== Exposure ==
The [[hepatotoxic]]ity of microcystin may cause serious damage to the [[liver]]. Once ingested, microcystin travels to the liver, via the bile acid transport system, where most is stored; though some remains in the blood stream and may contaminate tissue.<ref>Falconer, I.R. 1998. Algal toxins and human health. In Hrubec, J. (Ed.), Handbook of Environmental Chemistry, Volume 5 (Part C). Berlin: Springer-Verlag. Pp. 53-82.</ref><ref>Falconer, I.R. 2005. Cyanobacterial Toxins of Drinking Water Supplies: Cylindrospermopsins and Microcystins. Florida: CRC Press. 279 pages.</ref> There appears to be inadequate information to assess the carcinogenic potential of microcystins by applying EPA Guidelines for Carcinogen Risk Assessment. A few studies suggest a relationship may exist between liver and colorectral cancers and the occurrence of cyanobacteria in drinking water in China <ref>Humpage, A.R., Hardy, S.J., Moore, E.J., Froscio, S.M. & Falconer, I.R. 2000. Microcystins (cyanobacterial toxins) in drinking water enhance the growth of aberrant crypt foci in the colon. Journal of Toxicology and Environmental Health. (61) Pp 101-111.</ref><ref>Ito, E., Kondo, F., Terao, K. & Harada, K.-L. 1997. Neoplastic nodular formation in mouse liver induced by repeated intraperitoneal injection of microcystin-LR. Toxicon. (35) Pp 1453-1457.</ref><ref>Nishiwaki-Matushima, R., Nishiwaki, S., Ohta, T., Yoszawa, S., Suganuma, M., Harada, K., Watanabe, M.F. & Fujiki, H. 1991. Structure-function relationships of microcystins, liver-tumor promoters, in interaction with protein phosphatase. Japanese Journal of Cancer Research. (82) Pp 993-996.</ref><ref>Ueno, Y., Nagata, S., Tsutsumi, T., Hasegawa, A., Watanabe, M.F., Park, H.D., Chen, G.C. & Yu, S. 1996. Detection of microcystins in blue-green algae hepatotoxin in drinking water sampled in Haimen and Fusui, endemic areas of primary liver cancer in China, by highly sensitive immunoassay. Carcinogenesis. (17) Pp 1317-1321.</ref>(Yu et al., 1989; Zhou et al., 2002). Evidence is, however, limited due to limited ability to accurately assess and measure exposure.
The [[hepatotoxic]]ity of microcystin may cause serious damage to the [[liver]]. Once ingested, microcystin travels to the liver, via the bile acid transport system, where most is stored; though some remains in the blood stream and may contaminate tissue.<ref>{{cite book |first1=Ian R. |last1=Falconer |year=1998 |chapter=Algal Toxins and Human Health |editor1-first=Jiři |editor1-last=Hrubec |title=Quality and Treatment of Drinking Water II |series=The Handbook of Environmental Chemistry |pages=53-82 |doi=10.1007/978-3-540-68089-5_4}}</ref><ref>Falconer, I.R. 2005. Cyanobacterial Toxins of Drinking Water Supplies: Cylindrospermopsins and Microcystins. Florida: CRC Press. 279 pages.{{pn}}</ref> There appears to be inadequate information to assess the carcinogenic potential of microcystins by applying EPA Guidelines for Carcinogen Risk Assessment. A few studies suggest a relationship may exist between liver and colorectral cancers and the occurrence of cyanobacteria in drinking water in China <ref>{{cite journal |author=Humpage AR, Hardy SJ, Moore EJ, Froscio SM, Falconer IR |title=Microcystins (cyanobacterial toxins) in drinking water enhance the growth of aberrant crypt foci in the mouse colon |journal=Journal of Toxicology and Environmental Health, Part A |volume=61 |issue=3 |pages=155–65 |year=2000 |month=October |pmid=11036504 |doi=10.1080/00984100050131305}}</ref><ref>{{cite journal |author=Ito E, Kondo F, Terao K, Harada K |title=Neoplastic nodular formation in mouse liver induced by repeated intraperitoneal injections of microcystin-LR |journal=Toxicon |volume=35 |issue=9 |pages=1453–7 |year=1997 |month=September |pmid=9403968 |doi=10.1016/S0041-0101(97)00026-3}}</ref><ref>Nishiwaki-Matushima, R., Nishiwaki, S., Ohta, T., Yoszawa, S., Suganuma, M., Harada, K., Watanabe, M.F. & Fujiki, H. 1991. Structure-function relationships of microcystins, liver-tumor promoters, in interaction with protein phosphatase. Japanese Journal of Cancer Research. (82) Pp 993-996.</ref><ref>Ueno, Y., Nagata, S., Tsutsumi, T., Hasegawa, A., Watanabe, M.F., Park, H.D., Chen, G.C. & Yu, S. 1996. Detection of microcystins in blue-green algae hepatotoxin in drinking water sampled in Haimen and Fusui, endemic areas of primary liver cancer in China, by highly sensitive immunoassay. Carcinogenesis. (17) Pp 1317-1321.</ref>(Yu et al., 1989; Zhou et al., 2002). Evidence is, however, limited due to limited ability to accurately assess and measure exposure.


The impact of exposure to microcystin by patients with a compromised immune system is not yet fully known, but is starting to raise some concern.<ref>Doyle P. (1991). The Impact of AIDS on the South African Population. AIDS in South Africa: The Demographics and Economic Implications. Centre for Health Policy, University of the Witwatersrand, Johannesburg, South Africa.</ref>
The impact of exposure to microcystin by patients with a compromised immune system is not yet fully known, but is starting to raise some concern.<ref>Doyle P. (1991). The Impact of AIDS on the South African Population. AIDS in South Africa: The Demographics and Economic Implications. Centre for Health Policy, University of the Witwatersrand, Johannesburg, South Africa.</ref>

Revision as of 00:21, 4 August 2014

NOAA captured this view of Lake Erie in October 2011, during the worst blue-green algae bloom, the lake experienced in decades. Torrential rains, increased fertilizer runoff, and promoted the growth of the microcystin producing bacteria blooms.[1]

Microcystins are toxic peptides, produced in large quantities during blooms of the bacteria genus microcystis or planktothrix cyanobacteria (i.e. the species Microcystis aeruginosa).[2] Cyanobacterial blooms, can cause oxygen depletion, alter food webs, posing a major threat to drinking and irrigation water supplies, and to fishing and recreational use of surface waters worldwide.[3] Cyanobacteria blooms are often called blue-green algae, based on their appearance. Cyanobacteria are one of the oldest microorganisms on Earth, predating predators, 3.5 billion years ago and it is assumed they produced oxygen, building a living atmosphere.[4]

Characteristics

File:Microcystin-LR.png
Chemical structure of microcystin LR

Microcystin-LR is the most toxic form of over 80 known toxic variants, and is also the most studied by chemists, pharmacologists, biologists and ecologists. Microcystin-containing 'blooms' are a problem worldwide, including China, Brazil, Australia, South Africa,[5][6][7][8][9][10][11][12] the United States and much of Europe.

Microcystins consist of several uncommon non-proteinogenic amino acids such as dehydroalanine derivatives and the special β-amino acid ADDA, (all-S,all-E)-3-amino-9-methoxy-2,6,8-trimethyl-10-phenyldeca-4,6-dienoic acid). Microcystins can strongly inhibit protein phosphatases type 1 (PP1) and 2A (PP2A), and are linked to pansteatitis.[13] Microcystin binds covalently to protein phosphatases thus disrupting cellular control processes.

Exposure

The hepatotoxicity of microcystin may cause serious damage to the liver. Once ingested, microcystin travels to the liver, via the bile acid transport system, where most is stored; though some remains in the blood stream and may contaminate tissue.[14][15] There appears to be inadequate information to assess the carcinogenic potential of microcystins by applying EPA Guidelines for Carcinogen Risk Assessment. A few studies suggest a relationship may exist between liver and colorectral cancers and the occurrence of cyanobacteria in drinking water in China [16][17][18][19](Yu et al., 1989; Zhou et al., 2002). Evidence is, however, limited due to limited ability to accurately assess and measure exposure.

The impact of exposure to microcystin by patients with a compromised immune system is not yet fully known, but is starting to raise some concern.[20]

Formation

The microcystin producing microcystis, is a genus of freshwater cyanobacteria and is projected to thrive with warmer climate conditions, such as the rise of water temperatures or in stagnant waters, and through the process of eutrophication (oversupply of nutrients).[4] An Ohio state task force found that Lake Erie received phosphorus and more recently reactive phosphorus from crop land, due to the farming practices, and evidence suggests that in particular dissolved reactive phosphorus (from fertilizer) promotes additional growth.[21]

Pathways

Microcystin producing bacteria blooms, can overwhelm the filter capacities of water treatment plants. Some evidence shows the toxin can be transported by irrigation into the food chain,[22][23] but this still needs additional verification.

Cyanobacteria blooms

See also: Algal bloom and Water treatment

A study concluded in 2009 that climate change can act as a catalyst for global expansion of harmful cyanobacterial blooms.[3] The EPA reported in 2013, that changing environmental conditions such as harmful algae growth is associated with current climate change, and may negatively impact the environment, human health, and the economy for communities across the US and around the world.[24]

Recent developments

On 2 August 2014, the City of Toledo, Ohio detected higher levels of microcystin than deemed safe in its water supply due to harmful algal blooms (HABs) in Lake Erie, the shallowest of the Great Lakes. The affected water plant supplies approximately 500,000 people.[25][26] Algal blooms have been occurring more frequently, and scientists had predicted this significant bloom of blue-green algae, and they projected it to peak in early September.[27][28]

See also

References

  1. ^ Joanna M. Foster (November 20, 2013). "Lake Erie Is Dying Again, And Warmer Waters And Wetter Weather Are To Blame". ClimateProgress.
  2. ^ Neilan BA, Dittmann E, Rouhiainen L; et al. (1999). "Nonribosomal peptide synthesis and toxigenicity of cyanobacteria". Journal of Bacteriology. 181 (13): 4089–97. PMC 93901. PMID 10383979. {{cite journal}}: Explicit use of et al. in: |author= (help); Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
  3. ^ a b Paerl HW, Huisman J (2009). "Climate change: a catalyst for global expansion of harmful cyanobacterial blooms". Environmental Microbiology Reports. 1 (1): 27–37. doi:10.1111/j.1758-2229.2008.00004.x. PMID 23765717. {{cite journal}}: Unknown parameter |month= ignored (help)
  4. ^ a b "Increasing toxicity of algal blooms tied to nutrient enrichment and climate change". Oregon State University. October 24, 2013.
  5. ^ Bradshaw, D., Groenewald, P., Laubscher, R., Nannan, N., Nojilana, B., Norman, B., Pieterse, D. and Schneider, M. (2003). Initial Burden of Disease Estimates for South Africa, 2000. Cape Town: South African Medical Research Council.[page needed]
  6. ^ Fatoki, O.S., Muyima, N.Y.O. & Lujiza, N. 2001. Situation analysis of water quality in the Umtata River Catchment. Water SA, (27) Pp 467-474.
  7. ^ Oberholster PJ, Botha A-M, Grobbelaar JU (2004). "Microcystis aeruginosa: Source of toxic microcystins in drinking water". Africa Journal of Biotechnology. 3: 159–68.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  8. ^ Oberholster PJ, Botha A-M, Cloete TE (2005). "An overview of toxic freshwater cyanobacteria in South Africa with special reference to risk, impact and detection by molecular marker tools". Biokemistri. 17: 57–71. doi:10.4314/biokem.v17i2.32590.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  9. ^ Oberholster PJ, Botha A-M (2007). "Use of PCR based technologies for risk assessment of a winter cyanobacterial bloom in Lake Midmar, South Africa". African Journal of Biotechnology. 6 (15): 14–21.
  10. ^ Oberholster, P. 2008. Parliamentary Briefing Paper on Cyanobacteria in Water Resources of South Africa. Annexure “A” of CSIR Report No. CSIR/NRE/WR/IR/2008/0079/C. Pretoria. Council for Scientific and Industrial Research (CSIR).
  11. ^ Oberholster, P.J., Cloete, T.E., van Ginkel, C., Botha, A-M. & Ashton, P.J. 2008. The use of remote sensing and molecular markers as early warning indicators of the development of cyanobacterial hyperscum crust and microcystin-producing genotypes in the hypertrophic Lake Hartebeespoort, South Africa. Pretoria: Council for Scientific and Industrial Research (CSIR).
  12. ^ Oberholster, P.J. & Ashton, P.J. 2008. State of the Nation Report: An Overview of the Current Status of Water Quality and Eutrophication in South African Rivers and Reservoirs. Parliamentary Grant Deliverable. Pretoria: Council for Scientific and Industrial Research (CSIR).
  13. ^ http://www.pwrc.usgs.gov/health/rattner/rattner_blackwaternwr.cfm
  14. ^ Falconer, Ian R. (1998). "Algal Toxins and Human Health". In Hrubec, Jiři (ed.). Quality and Treatment of Drinking Water II. The Handbook of Environmental Chemistry. pp. 53–82. doi:10.1007/978-3-540-68089-5_4.
  15. ^ Falconer, I.R. 2005. Cyanobacterial Toxins of Drinking Water Supplies: Cylindrospermopsins and Microcystins. Florida: CRC Press. 279 pages.[page needed]
  16. ^ Humpage AR, Hardy SJ, Moore EJ, Froscio SM, Falconer IR (2000). "Microcystins (cyanobacterial toxins) in drinking water enhance the growth of aberrant crypt foci in the mouse colon". Journal of Toxicology and Environmental Health, Part A. 61 (3): 155–65. doi:10.1080/00984100050131305. PMID 11036504. {{cite journal}}: Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
  17. ^ Ito E, Kondo F, Terao K, Harada K (1997). "Neoplastic nodular formation in mouse liver induced by repeated intraperitoneal injections of microcystin-LR". Toxicon. 35 (9): 1453–7. doi:10.1016/S0041-0101(97)00026-3. PMID 9403968. {{cite journal}}: Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
  18. ^ Nishiwaki-Matushima, R., Nishiwaki, S., Ohta, T., Yoszawa, S., Suganuma, M., Harada, K., Watanabe, M.F. & Fujiki, H. 1991. Structure-function relationships of microcystins, liver-tumor promoters, in interaction with protein phosphatase. Japanese Journal of Cancer Research. (82) Pp 993-996.
  19. ^ Ueno, Y., Nagata, S., Tsutsumi, T., Hasegawa, A., Watanabe, M.F., Park, H.D., Chen, G.C. & Yu, S. 1996. Detection of microcystins in blue-green algae hepatotoxin in drinking water sampled in Haimen and Fusui, endemic areas of primary liver cancer in China, by highly sensitive immunoassay. Carcinogenesis. (17) Pp 1317-1321.
  20. ^ Doyle P. (1991). The Impact of AIDS on the South African Population. AIDS in South Africa: The Demographics and Economic Implications. Centre for Health Policy, University of the Witwatersrand, Johannesburg, South Africa.
  21. ^ Suzanne Goldenberg (August 3, 2014). "Farming practices and climate change at root of Toledo water pollution". The Guardian.
  22. ^ Codd, G.A,, Metcalf, J.S. & Beattie, K.A. 1999. Retention of Microcystis aeruginosa and microcystin by salad lettuce after spray irrigation with water containing cyanobacteria. Toxicon, (37) Pp. 1181-1185.
  23. ^ Abe, T., Lawson, T., Weyers, J.D.B,, & Codd, G.A. 1996. Microcystin-LR inhibits photosynthesis of Phaseolus Vulgaris primary leaves: implications for current spray irrigation practice. New Phytol. 133: 651-658.
  24. ^ "Impacts of Climate Change on the Occurrence of Harmful Algal Blooms" (PDF). EPA. 2013.
  25. ^ "Algal bloom leaves 500,000 without drinking water in northeast Ohio". Reuters. August 2, 2014.
  26. ^ Rick Jervis, USA TODAY (August 2, 2014). "Toxins contaminate drinking water in northwest Ohio".
  27. ^ John Seewer. "Don't drink the water, says 4th-largest Ohio city".
  28. ^ "Toxins in water leads to state of emergency in Ohio". Ohio Standard. Retrieved 2 August 2014. {{cite news}}: Italic or bold markup not allowed in: |publisher= (help)
  • National Center for Environmental Assessment. Toxicological Reviews of Cyanobacterial Toxins: Microcystins LR, RR, YR and LA (NCEA-C-1765)
  • Yu, S.-Z. 1989. Drinking water and primary liver cancer. In: Primary Liver Cancer, Z.Y. Tang, M.C. Wu and S.S. Xia, Ed. China Academic Publishers, New York, NY. p. 30-37 (as cited in Ueno et al., 1996 and Health Canada, 2002).
  • Zhou, L., H. Yu and K. Chen. 2002. Relationship between microcystin in drinking water and colorectal cancer. Biomed. Environ. Sci. 15(2):166-171.

External links

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