The natural occurrence of
arsenic in ground water constitutes a setback in the provision of safe drinking
water to millions of citizens in Asia. At least 60 million people live in
arsenic -affected regions and many drink arsenic-contaminated water on the daily
basis. Pakistan Council of Research in Water Resources (PCRWR), has conducted
several research studies to identify and quantify arsenic contamination of
ground water being used for domestic, agricultural, and industrial consumption
specifically in Punjab and Sindh provinces. Arsenic ingestion is often estimated
from water intake alone, although it is increasingly apparent that an additional
loading arises from arsenic in food, especially from paddy rice grown with
contaminated irrigation water. Soils thus irrigated may accumulate arsenic to
phytotoxic levels, creating a problem of latent effects on crop yields.
Arsenic is a highly toxic element that is naturally present in higher levels in
ground water drawn from alluvial soils (i.e. those deposited by rivers). The
Indus valley is therefore one of the regions in the world where this hazard is
ever present. In Pakistan arsenic contamination is prevalent mainly in Punjab
and Sindh provinces, and the hazard in drinking water drawn from wells is well
known. However, hew research has recently come to light indicating that arsenic
can be toxic over the longer term at levels much lower than previously
considered. As a result there are new concerns regarding the total dietary
exposure to this element, and this has raised the issue of the safety of some
food crops which may be grown in affected areas when irrigated with ground
Most investigations have focused on the arsenic risk from drinking water, but
there is now widening interest in whether this poison can also be passed on in
rice, through irrigated fields. Human exposure to arsenic (As) via rice
consumption is of increasing concern. Rice is one of the most important food
crops around the world and feeds over half of the global population.
Pakistan being an agro-based economy has natural abundance of all agricultural
products including food items. Rice is the third largest crop after wheat and
cotton. It is grown over 10% of the total cropped area and is highly valued cash
crop as well as major export item. It accounts for 6.7% in value added in
agriculture and 1.6% in GDP. Pakistan grows enough high quality rice to meet
both domestic demand and allow for exports of around one million ton per annum.
Pakistan exported about 3.4 million tonnes of rice in 2012, earning about US$1.8
billion. The establishment of international limits on arsenic in rice could
potentially impact on this important export market for Pakistan.
On the basis of the occurrence data collected, the preliminary findings of this
study have revealed that arsenic contamination risk from irrigation water to
food chain has not reached alarming proportions yet, however; there is a need to
deal with the possible threats posed by arsenic contaminated irrigation water.
Distribution of arsenic in major rice varieties specifically of export quality
is not a critical concern at present. However, the results of this study calk
for careful implementation of the irrigation system modernization taking ground
water quality in due consideration.