Paul et.al.
Arsenic contamination of the environment can
Plants take up As from soil and are known to
also occur through the use of arsenical fungicides,
accumulate in different parts depending on the
herbicides, and insecticides in the agriculture
speciesandvariety.Arsenicaccumulatedintheedible
(Bissen and Frimmel 2003). Soil contamination
parts of plants may result food chain contamination
due to the use of organoarsenical herbicides such
and pose serious health risk to humans (Abedin et
as monosodium methanearsonate (MSMA) and
al. , 2002). The World Health Organization (WHO
disodium methanearsonate (DSMA) was also
1993) has set a value of 2g As kg −1 bodyweight/day
reported (Gilmore and Wells 1980; Smith et al. , 1998).
as the tolerable daily intake. However, in countries
The use of sodium arsenite (NaAsO 2 ) to control
where most of the basic diet consists of cereals and
aquatic weeds has contaminated small fish ponds
vegetables, the stated value is not observed when
and lakes in several parts of United States with As
cropland or irrigation water contain high levels of
(Adriano 2001).
As (Sengupta et al. , 2006; Signes-Pastor et al. , 2008).
The As content of rice grain is an important concern
Impacts on Agriculture and Food Chain
because of the large daily intake of rice by people
Long term use of As based fungicides, pesticides
in many parts of S and SE Asia (commonly assumed
and insecticides as well as irrigation with As
to be 450 g day -1 for a 60 kg adult in Bangladesh).
contaminated ground water had led to elevated
Duxbury and Zavala (2005) pointed out that, when
concentration of As in soil. Bioavailability of As to
As in rice grain exceeds 0.11 mg kg -1 , it is possible
plant species is highly influenced by several soil
for adults consuming 450 g of rice and 4 L of water
factors including redox potential, pH, the contents
per day at the 10 ppb WHO As water standard to
of organic matter, iron, manganese, phosphorus,
exceed the FAO and WHO provisional tolerable
calcium-carbonate, soil microbes and the speciation
dietary intake standard of 130 μg As per day for a 60
of As in soil (Mahimairaja et al. , 2005). Marin et al. ,
kg adult. Williams et al. , (2006) measured As contents
(1992) reported that the order ofAs availability to rice
of 37 vegetables, pulses and spices commonly grown
(Oryza sativa) is as follows: As(III) > MMA > As(V)
in Bangladesh and found that As levels were highest
> DMA. Although plants exhibit certain degree of
in radish leaves (0.79 mg kg -1 ), arum stolons, spinach
tolerance to As, at higher concentration As is toxic
and cucumber, and lowest (0.2 mg kg -1 ) in most
to all forms of life. An average toxicity threshold of
fruits, vegetables, and spices. Besides As intake
40 mg As kg -1 biomass has been established for crop
from cereals and vegetables, consumption of certain
plants (Sheppard 1992).Arsenic is known to alter and
seafood and fish can be potential sources of As intake
disturb uptake and transport of nutrients in plants
(Peralta-Videa et al. , 2009). According to Rose et al. ,
(Päivöke and Simola 2001) leading to yield loss.
(2007), As is first accumulated in phytoplankton
Various other symptoms of phytotoxicity include
from sea water and transformed into arsenosugar
retardation of root and shoot growth (Macnair
compounds and DMA, which are taken up by algae.
andand Cumbes 1987; Meharg andand Macnair
Arsenosugar compounds are then transformed to
1991), inhibition of root water uptake and ultimately
arsobetaine by methylation of As (V), MAA, and
resulting in death from wilting (Woolson et al. , 1971).
DMA by microbial organisms (Peralta-Videa et al. ,
Rice being produced in As contaminated soil showed
2009). The As levels can be magnified 1000–10,000-
symptoms of straight head disease which included
fold in marine animals that ingest algae (Borak
increased sterility (Wells and Gilmour, 1977). There
and Hosgood 2007). Furthermore, bivalves such as
is significant evidence that exposure to inorganic As
oysters, mussels and clamswere found to accumulate
species results in the generation of reactive oxygen
arsenosugar-PO4 and arsenobetaine, which are less
species (ROS) which leads to oxidative stress in
toxic than inorganic As compounds. The dietary
plants (Hartley-Whitaker et al. , 2001).
intake of organoarsenic compounds via seafood pose
little health risk to animals and humans, because
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