Arsenic toxicity and speciation in plants, Arsenic toxicity and speciation in plants, Arsenic toxicity and speciation in plants, Arsenic toxicity and speciation in plants, implications for human nutrition implications for human nutrition Lecture of Seema Mishra in the VK Bioinorganic Chemistry & Biophysics of Plants 2012
28
Embed
SM Arsenic toxicity and speciation in plants implications ...€¦ · Arsenic toxicity and speciation in plants, implications for human nutrition Lecture of Seema Mishra in the VK
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Arsenic toxicity and speciation in plants, Arsenic toxicity and speciation in plants, Arsenic toxicity and speciation in plants, Arsenic toxicity and speciation in plants, implications for human nutrition implications for human nutrition
Lecture of Seema Mishra in the VK Bioinorganic Chemistry & Biophysics of Plants 2012
ArsenicArsenic
ArsenicArsenic
2, 8, 18, 5
Arsenic: occurrence Arsenic: occurrence
As is the twentieth most abundant element in the Earth’s crust with an average concentration of approximately 3 mg kg−1average concentration of approximately 3 mg kg 1.
More than 200 As-containing minerals exist; frequently As is associated with S in minerals such as arsenopyrites (FeAsS), realgar (As4S4), and orpiment (As2S3).
Arsenopyrites Realgar Orpiment
Arsenic: ApplicationsArsenic: Applications
The Poison of Kings and the King of Poisons Semiconductor industries Strengthening alloys of copper and lead Pesticides herbicides insecticides Pesticides, herbicides, insecticides Wood preservatives Feed additives Medical uses Military uses
Arsenic trioxide
Structures of the most common As compounds
Trimethyl Arsiney
Sources of Arsenic ContaminationSources of Arsenic Contamination
Through anthropogenic activities such as mining, smelting, phosphate fertilizer, and the use of As-containing pesticides, herbicides, wood preservatives, and feed additives.
Through natural processes such as weathering of rocks volcanic Through natural processes, such as weathering of rocks, volcanic emissions and discharge from hot springs
Arsenic ContaminationArsenic Contamination
Arsenic ContaminationArsenic Contamination
Basic Facts of the ProblemBasic Facts of the Problem
The current limit of As in drinking water (WHO) is 10 μg/L.
WHO Provisional Maximum Tolerable Daily Intake (MTDI) limit of As is 2 μg/Kg body weight.μg g y g
Level of As in drinking in West Bengal above 50 μg/L are commonly found Severely affected areas may contain as high as 2000 μg/Lfound. Severely affected areas may contain as high as 2000 μg/L.
If rice grain with an As level of 0.1 μg/g (a typically normal As level) is consumed at a rate of 420 g/day (representative of rice-based diet), then ingestion of 0.7 μg/Kg (35% of MTDI) body weight would occur.
Far exceeding levels e.g. up to 3 μg/g are found. In addition, cooking rice in contaminated water also adds to As consumption.
Arsenic ExposureArsenic Exposure
Toxicity to human Toxicity to human
Acute effects Gastrointestinal effects (Nausea Diarrhea Abdominal pain) Gastrointestinal effects (Nausea, Diarrhea, Abdominal pain) Effects on central nervous system and cardiovascular system Liver and kidney dysfunction Anemia, leukopenia Ingestion of 600 µg/kg body weight/day or inhalation of 25-50 ppm
arsine for a half- hour is lethalarsine for a half hour is lethal Chronic effects Gastrointestinal effects, Skin lesions, hyperpigmentation, Anemia, peripheral neuropathy, gangrene of the extremities, vascular
lesions, and liver or kidney damage, y g Increased risk of Cancer : skin, bladder, liver, and lung cancer
Toxicity to human Toxicity to human
(www.soesju.org)Richard Wilson, Harvard University, and Dhaka Community Hospital
Arsenicosis patients from arsenic-affected areas
Why Rice ?Why Rice ?
Pick your poison ?
Why Rice ?Why Rice ?
Meharg (2004). TRENDS in plant science, 9, 415-417.
Arsenic Toxicity to Plants Arsenic Toxicity to Plants
New Bacteria Makes DNA With Arsenic: NASA Life Discovery
The arsenic rich Mono Lake California A scanning electron micrograph ofThe arsenic-rich Mono Lake, California A scanning electron micrograph of the arsenic-based bacteria
A Bacterium That Can Grow by Using Arsenic Instead of Phosphorus
Wolfe-Simon et al (2011), Science. 332, 1163-1166
A Bacterium That Can Grow by Using Arsenic Instead of Phosphorus
Can arsenic bind to bacterial DNA ?
DNA structure with arsenic replacing phosphorus in the backboneJ Wang, J Gu and J Leszczynski, Chem. Commun., 2012, DOI: 10.1039/c2cc16600c