Results And Discussion
4.1 ARSENIC IN WATER
In Bangladesh, the groundwater As contamination problem is the worst in the world. Ninety-seven percent of the population in the country uses groundwater for drinking and domestic purposes as surface water is mismanaged. (Hossain, 2006). Levels of arsenic in drinking water are so high that WHO describes arsenic contamination of Bangladesh's water supply as "the largest poisoning of a population in history". (FAO, 2000)
It has been suggested that there are between 8-12 million shallow tube-wells in Bangladesh. Up to 90% of the Bangladesh population of 130 million prefers to drink well water. Piped water supplies are available only to a little more than 10% of the total population living in the large agglomerations and some district towns. (WHO, 2001)
In the present study the mean total arsenic concentration in tube well water was found 63.00 µg/l and 82.50 µg/l for HTW*-1and HTW-2 respectively. Both results shown the arsenic concentration above the Bangladesh drinking water standard (50µg/l) (BGS and DPHE, 2001) and WHO’s standard (10 µg/l) (WHO, 1985). Accordingly for the river water and pond water, the mean total arsenic concentration was 36.00µg/l (RW**-1) and 35.50 µg/l (RW-2) and 6.00µg/l respectively.( * Hand tube well, ** River water)
The highest concentration was found in tube well water and HTW-2 is the most contaminated compared to that of the HTW-1. The lowest concentration was found in pond water.
The mean concentration of arsenic in various water samples including total arsenic in three replications are shown in figure 8.
Figure -8: Level of arsenic concentration in water samples
4.2 ARSENIC IN AGRO CROP AND IT’S CORRESPONDING SOIL
Crops receiving AS contaminated irrigation water can uptake As element during the phytoextraction process and bio-accumulate in different degrees at different
parts of plants (eg. roots, stems, and grains). Researchers found high concentrations of As in vegetables and rice in areas where concentrations of As in soil and water are also high. Therefore, the food chain could be a significant pathway of As ingestion by Bangladesh people. (Kibria, 2006). The average background concentration of arsenic in Bangladesh is much below 10 mg/kg soil. However, in some areas where soils receive As-contaminated ground water irrigation, the concentration has been found to be as high as 80 mg/kg soil. (Inamul, 2005).
Our investigation shows the mean As concentration in rice grain as 0.365 mg/kg. The total As concentration followed the trend with variety as cv. BR-29> cv. BR-28> L.cv. Shishumoti. As cv. BR-29 is a long-term (160 days*) variety, so the arsenic uptake is also high in this and as L.cv. Shishumoti is a local variety (110-120* days) so it uptakes arsenic comparatively less than others. The duration of BR-28 is 140* days. The concentrations are not exceeded the Australian food hygiene limit of 1.0 mg/kg. (Ali, Sine datum). (*Source- ‘Agriculture diary’ published by Agriculture Information Service, 2006)
On the other hand, the rice straw shows the mean concentration as 1.610 mg/kg. The varieties shows the trend of total concentration as same as the rice grain because they are of the same origin. The total concentrations of arsenic in rice grain and straw in different varieties are shown in figure 9 and 10.
Figure -9: Total arsenic concentration in rice grain of different varieties
Figure -10: Total arsenic concentration in rice straw of different varieties
Corresponding soil was taken from the paddy field. The mean arsenic concentration in soil sample is 12.64 mg/kg. The soil collected from the BR-28 field shows the highest (13.07mg/kg) concentration of arsenic and the lowest in BR-29 variety (12.32 mg/kg). Shishumoti shows the concentration as 12.51 mg/kg.
The possible reason behind it is that, BR-29 is a long-term variety compared to BR-28. Therefore, with the passing of time, it (BR-29) uptakes much amount of arsenic from the soil. However, it is fully reversed in case of BR-28 variety. Again shishumoti is a local variety and it uptakes arsenic naturally in less amount (though it is now being under research) from soil. However, the total soil arsenic has already exceeded the average background concentration. The arsenic concentration in soil samples are shown in figure 11.
Figure -11: Total arsenic concentration in corresponding soil of different rice varieties
As referred by Meharg and Hartley-Whitaker (2002), for example, a specific form of arsenic toxicity to rice known as straighthead disease has been reported in the United States. This observation was related to rice production on former cotton fields heavily contaminated with MMA (Monomethylarsonic Acid ) used as a herbicide. It was most frequently observed on sandy loam soils but seldom on clay soils. Affected plants usually found in spots scattered throughout a field. Straighthead disease is a physiological disorder that causes panicle sterility. Visual symptoms are empty panicles standing upright instead of bending downward at maturity.
Carbonell et al. (1998) found that Phosphorus (P) was reduced in the roots of rice plants when exposed to As ш or As v, while P in the shoots was increased.
Among the vegetables samples the total arsenic concentration in kachu is 0.241 and 0.202 mg/kg for sample 1 and 2 respectively. For cabbage, it is 0.196 and 0.221 mg/kg respectively. The highest concentration was found in lalshak. The concentration is 0.329 and 0.302 mg/kg for sample 1 and 2 respectively.
Corresponding soil from each of the vegetable field was collected. The total arsenic concentration is 11.17 mg/kg for kachu, 11.48 mg/kg for lalshak and 13.01 mg/kg for cabbage. All samples show the crossed limit of average background arsenic concentration in soil. The total arsenic concentration of the vegetables and their corresponding soil samples are shown in figure 12 and 13.
Figure -12: Total arsenic concentration in different vegetables samples
Figure -13: Total arsenic concentration in corresponding soils of different vegetables
Edible portions of plants seldom accumulate high concentrations of arsenic. This is because most backyard vegetable plants are sensitive to arsenic in soil and will either be killed or severely stunted long before the arsenic concentrations in their tissues reach concentrations that pose a health risk. The extent of arsenic uptake into plants not only depends on the degree of arsenic contamination in the soil but also on soil properties. In general, the sandier or wetter the soil, the greater the potential for arsenic toxicity. Toxicity symptoms in plants include stunted, blackened roots and blackened leaf margins. (Ministry of the Environment programs and initiatives, March 2001).
Soil microorganisms may also be affected by arsenic toxicity. (Mahimairaja et al. 2005). Effects of arsenic and on the soil microbial community can be expected, with As ш being more toxic than As v. Microbes can adapt to arsenic contamination, but this can be accompanied by a change in density and structure of the community. Ghosh et al. (2003) reported that microbial biomass and activity were negetavily correlated with total and bioavailable arsenic in soil samples from West Bengal.
4.3 ARSENIC IN LIVESTOCK
Arsenic is an approved animal dietary supplement and is found in specifically approved drugs added to poultry and other animal feeds.
People who eat chicken may be taking in greater amounts of arsenic than anyone has previously thought. Arsenic concentrations in young chickens are three times greater than in other meat and poultry products, U.S. government scientists report in the January issue of "Environmental Health Perspectives." (Bethesda, 2004).
Animals are able to tolerate low levels of arsenic; the normal level in cattle tissues is <0.5> 10 to 15 ppm in the liver, accompanied by clinical signs, are considered diagnostic of acute arsenic toxicosis (Fletcher, 1986).
In our study, all the livestock samples were analyzed for total arsenic on fresh weight basis. The investigation shows that, the total arsenic in beaf liver is 161.71 µg/kg and in muscle is 96.04 µg/kg. Accordingly, in chicken liver and muscle, the total arsenic is 87.14 µg/kg and 54.04 µg/kg respectively. Goat liver shows the arsenic concentration as 120.16 µg/kg. Again muscle shows the arsenic concentration as 85.23 µg/kg.
If we look at our results, we will see that the concentration is higher in liver than muscle. I.e. liver is more affected than muscle. Again among all categories cow is the most affected in terms of both liver and muscle. The total concentration of arsenic is shown in figure 14.
Figure -14: Level of total arsenic in livestock samples
Arsenic poisoning in livestock may be peracute, with clinical signs including depression, prostration, and sudden death. Chronic arsenic poisoning is rarely seen in domestic animals because arsenic is rapidly excreted in the urine. Arsenic may be absorbed percutaneously, causing blistering, edema, and necrosis of the skin due to capillary dilatation and degeneration. The trivalent form of inorganic arsenic is up to 10 times more toxic than the pentavalent form and causes most of the toxic effects. Trivalent inorganic arsenic binds to and inactivates intracellular sulfhydryl-containing compounds, especially lipoic acid and α-keto oxidases, thereby disrupting cellular metabolism and inhibiting enzyme systems essential for oxidative phosphorylation. The tissues of most organs affected by arsenic have high oxidative energy requirements, principally the alimentary tract, kidney, liver, lung, brain, and epidermis. This disruption in energy metabolism may have caused the ataxia. Arsenic also affects capillary integrity through an unknown mechanism. Increased permeability of capillaries systemically allows for transudation of plasma fluid into the gastrointestinal tract, which causes submucosal congestion, edema, diarrhea, dehydration, acidosis, and shock.
4.4ARSENIC IN HUMAN
Arsenic contamination of groundwater in Bangladesh threatens the health of up to 30 million people. Now, a report from FAO suggests that arsenic in groundwater may pose an even more insidious threat. From a major review of studies conducted in Bangladesh, and elsewhere in Asia, the report concludes that people may be exposed to arsenic not only through drinking water, but indirectly though food crops irrigated by contaminated groundwater. (Arsenic threats, 2006). The highest level of arsenic concentration in human body is 0.89 mg/kg for nail and 0.18 mg/kg for hair. (Abernathy, Sine datum).
The present study works on two target people (Yunus and Hashem) for arsenic determination whose social statuses are also different. The investigation shows the arsenic concentration in Yunus’s hair 0.857 mg/kg and nail 1.766 mg/kg. Hashem’s hair and nail samples show the arsenic concentration as 0.943 mg/kg and 5.042 mg/kg respectively.
It is clearly observed that arsenic concentration exceed their highest limit for both men. Again, between the two people Hashem is most affected compared to Yunus. The main thing is that Yunus is a well-established farmer and his monthly income is approximately 15,000 tk. He eats food that is more nutritious in his daily intake and gets proper medical treatment. On the other hand, Hashem is a rickshaw puller and his monthly income is nearly 3,000 tk. He does not get the above facilities. As a result, he is already suffered from Arseniocosis (shown in figure 14). However, in case of Yunus this symptom is still invisible. But probably he may get injured within next 5 or 10 years. The total arsenic in hair and nail samples are shown in figure 16.
Figure -15: A patient with Arseniocosis symptom
Figure -16: Arsenic concentration in human's hair and nail
With some 35 to 57 million people drinking arsenic-contaminated water, Bangladesh is experiencing a serious health hazard. The exact number of people suffering from arsenicosis in Bangladesh is still not known. As of 2002, over 10,000 cases of arsenicosis have been identified. (Moinuddin, Sine datum) Part5
Breathing high levels of inorganic arsenic can give a sore throat or irritated lungs. Ingesting very high levels of arsenic can result in death. Exposure to lower levels can cause nausea and vomiting, decreased production of red and white blood cells, abnormal heart rhythm, damage to blood vessels, and a sensation of “pins and needles” in hands and feet. Ingesting or breathing low levels of inorganic arsenic for a long time can cause a darkening of the skin and the appearance of small “corns” or “warts” on the palms, soles, and torso. Skin contact with inorganic arsenic may cause redness and swelling. Almost nothing is known regarding health effects of organic arsenic compounds in humans. Studies in animals show that some simple organic arsenic compounds are less toxic than inorganic forms. Ingestion of methyl and dimethyl compounds can cause diarrhea and damage to the kidneys. Several studies have shown that ingestion of inorganic arsenic can increase the risk of skin cancer and cancer in the liver, bladder, and lungs. Inhalation of inorganic arsenic can cause increased risk of lung cancer. The Department of Health and Human Services (DHHS) and the EPA have determined that inorganic arsenic is a known human carcinogen. The International Agency for Research on Cancer (IARC) has determined that inorganic arsenic is carcinogenic to humans. There is some evidence that long-term exposure to arsenic in children may result in lower IQ scores. There is also some evidence that exposure to arsenic in the womb and early childhood may increase mortality in young adults. There is some evidence that inhaled or ingested arsenic can injure pregnant women or their unborn babies, although the studies are not definitive. Studies in animals show that large doses of arsenic that cause illness in pregnant females, can also cause low birth weight, fetal malformations, and even fetal death. Arsenic can cross the placenta and has been found in fetal tissues. Arsenic is found at low levels in breast milk. (ATSDR, 2001)
4.6 ARSENIC IN FOREST CROP AND IT’S CORRESPONDING SOIL
Forest is one of the major parts of biodiversity. It plays a significant role in giving environment for the survival of other biological components. Therefore, like others it is also very much important to determine the level of arsenic concentration in forest tree species. However, this work has not been conducted yet so far in our country, but our investigation tried to determine this.
According to our investigation, Eucalyptus shows the highest total arsenic (0.127 mg/kg) in their wood. Mehogoni shows the arsenic concentration as 0.105 mg/kg. The total arsenic in Sissoo is 0.098 mg/kg. The lowest arsenic concentration was reported from Akashmoni species (0.074 mg/kg).
Corresponding soil was also collected from the ground of each of the tree species. From the soil samples, the highest concentration was reported from Akashmoni (12.53 mg/kg). Mehogoni shows the arsenic concentration as 9.33 mg/kg. Total arsenic 8.19 mg/kg was reported from Sissoo species. The lowest concentration was found in Eucalyptus species (7.83 mg/kg).
One of the interesting findings we have found from this result is that, Eucalyptus shows the highest concentration in wood but in corresponding soil, the concentration is the lowest. i.e. Eucalyptus uptake arsenic from soil in much amount. As a result, soil arsenic is low. However, in case of Akashmoni it is fully reversed. Akashmoni shows the lowest concentration in wood but in soil, it is the highest. i.e. it uptakes arsenic from soil in less amount compared to Eucalyptus. As a result, soil arsenic is high. Mehogoni and Sissoo follow the same trend in both wood and soil in terms of concentration. The descending arrangement of wood samples are Eucalyptus> Mehogoni> Sissoo> Akashmoni. For soil samples these are Akashmoni> Mehogoni> Sissoo> Eucalyptus. The total arsenic concentration of the wood and their corresponding soil samples are shown in figure 17 and 18.
Figure -17: Total arsenic concentration in wood
Figure -18: Total arsenic concentration in corresponding soil of different forest crop
4.7 ARSENIC IN AQUATIC ANIMAL (FISH)
Fish is one of the most important components of aquatic biodiversity. In Bangladesh, it is a common item of our daily intake. Puti, a local species of our country is used for our investigation.
The mean arsenic concentration in puti fish is found to be 130.32 µg/kg. The concentration of arsenic in fish are shown in figure 19.
Figure -19: Total arsenic concentration in fish
