Toxic chemical build-up in NCP, upcountry soils:
Cadmium poison threat looms
Cadmium is a Class 1 carcinogen according to the International Agency
for Research on Cancer of the World Health Organization, and is also a
well known nephrotoxin, meaning that it could impair kidney functions.
The WHO and the Ministry of Health concluded that cadmium is a risk
factor for the Chronic Kidney Disease of unknown Etiology (CKDu) from a
joint study they conducted in 2011 and 2012.
The Sri Lankan public needs to be informed about the presence of
cadmium in the environment. Sri Lankan scientists need to urgently
engage in research on the subject and, we need to invest sufficiently in
a cadre of environmental scientists as a matter of high priority.
Much of the information given here is from published literature. The
sources can be provided to interested readers via email.
Even in the early 1950s most of the people living in Anuradhapura
district drank surface water mainly from the large number of small tanks
that existed in most of the villages. It is after the Mahaveli river
diversion that many people shifted to drinking well water. At present
almost every farm family in Systems B and C has its own well. Many
living in the cities in the district have access to pipe-borne water. It
can be said that there is hardly a publication in the last five years
that reported values of cadmium in drinking water that exceeded the safe
limit of 0.003 mg/litre stipulated by the Sri Lanka Standards Institute
(SLSI). Most of the values were less than 0.002 mg/litre.
It is likely that the cadmium content in ground water is mostly due
to geogenic factors (geological processes). The anthropogenic cadmium
(due to human activity) such as from triple superphosphate fertilizer
(TSP) that is added to the soil surface, has to travel a long distance
through top soil, sub soil, decomposing rock and other materials before
reaching ground water.
In this journey the soluble cadmium can be rendered sparingly
soluble. It is therefore not surprising that cadmium levels in ground
water are low.
In fact many studies in other countries have shown that cadmium
hardly moves below a depth of about 40 cm from the soil surface..
Although drinking water cadmium levels are lower than the SLSI limit
at present, there is no guarantee that this situation will last for a
long time. There is published information showing that the phosphorus
levels in some of the reservoirs in Anuradhapura and Polonnaruwa
districts have increased five fold from the values reported fifty years
ago. This is perhaps mainly due to the use of excessive amounts of
phosphate fertilizer in the upcountry. If phosphorus in the reservoir
waters have increased and are increasing, it follows that although
cadmium is low at present, it too may be increasing, given that all
phosphate fertilizers contain cadmium.
It is not only the current values of cadmium in drinking water that
have to be taken note of, but also the rate of change. The country
should continuously monitor the content of potential toxins in all water
bodies whether they are likely to be the causal factor of CKDu or not.
Cadmium in soil
There is hardly any published information regarding high levels of
cadmium in soils reported from any part of the world arising from
geogenic factors . Much of the contamination has been shown to be
anthropogenic. New Zealand had a very serious cadmium contamination of
their pasture lands in the 1980s that resulted in a severe crisis in the
livestock industry. Investigations revealed that it was caused by the
use of high-cadmium containing phosphate fertilizers manufactured from
Nauru rock phosphate.
Many vegetable growing farmers in the upcountry have been adding 8-10
times the Department of Agriculture chemical fertilizer recommendation
for over two decades. The main reasons for this unfortunate situation
include the extremely high profits from cultivating potato and other
vegetables, very low prices of subsidised chemical fertilizers and a
complete breakdown of a well established agricultural extension
service.The combined effect of these factors has led to the rapid
build-up of soil phosphorus to an extent probably not found elsewhere in
the world. More details of this agronomic, economic and environmental
disaster are described in a book by the writer published in 2015 by the
National Water Supply and Drainage Board (Ref 1).
Lakmalie Wijeratne in her MPhil Thesis submitted to the Postgraduate
Institute of Agriculture, University of Peradeniya, (titled Soil and
Crop Contamination by Toxic Trace Elements) has reported the Olsen
phosphorus values of a number of soil samples collected from the
upcountry and lowcountry vegetable growing lands. This is a measure of
phosphorus in soil that is available for plant growth. It hardly exceeds
20 mg/kg in uncultivated lands. A value of 30-40 mg/kg soil is normally
considered adequate for crops. The research findings indicated that
vegetable growing farmers have added excessive amounts of
phosphate-containing fertilizers in the upcountry and the low country.
There is hardly a phosphate fertilizer in the world that does not
contain cadmium. The quantity however, varies widely from 3 mg/kg in
Florida rock phosphate in USA to over 100 mg/kg in Nauru. There is
published evidence from Australia, New Zealand and many countries in
Europe showing that elevated levels of cadmium in soils have arisen from
the application of phosphate fertilizers over long periods of time.
The MPhil research referred to above gives the cadmium content of
soil samples collected from vegetable cultivating lands in the upcountry
and the lowcountry.
In the upcountry 18 samples were studied from Seetha Eliya, Kandapola,
Haputale, Bogahakumbura and Rahangala. The average cadmium value was
1.21 mg/kg. The uncultivated soil had only 0.51 mg/kg cadmium.Twenty two
locations were studied at Bandaragama and Wellampitiya in the low
country. The average cadmium value was 1.10 mg/kg soil. The
corresponding value for uncultivated soil was 0.03 mg/kg. One could
conclude from these studies that soil cadmium content of vegetable
cultivated lands has increased in the upcountry and the lowcountry in
These results suggest strongly that the build-up of cadmium in soils
of some areas in Sri Lanka has been caused by the addition of high
levels of phosphate containing fertilizers, as has been observed in many
More than half a dozen factors can affect the cadmium content of the
soil solution. They include; soil minerals, soil clays, low molecular
weight organic acids, iron and aluminium oxides, chloride from potash
fertilizer and irrigation water, sewage sludge and phosphate fertilizer.
Research conducted on soil cadmium with respect to its chemistry and
dynamics in tropical countries is scarce.
Cadmium in vegetables
The same MPhil research reports the cadmium content of above ground
parts of a number of vegetables grown in the upcountry and lowcountry.
The cadmium content of carrot, cabbage, leek and lettuce ranged from
0.30 to 2.71 with an average value of 0.93 mg/kg.
The cadmium content of kang kung, mukunuwenna, sarana, spinach,
thampala and gotukala was determined from 18 locations in Wellampitiya
and Bandaragama in the low country. The values ranged from 0.17 to 1.10
with an average value of 0.47 mg/kg. Much of the cadmium of vegetables
is very likely coming from the application of TSP fertilizer, cow dung
and poultry litter.
Many countries have regulations in place to prohibit entry of
high-cadmium containing fertilizers. It is only In 1988 that the Sri
Lanka Standards Institute (SLSI) issued a Circular stating that
phosphate fertilizers containing more than 5 ppm (parts per million)
cadmium will not be permitted into the country.
Prior to that Sri Lanka may have imported hundreds of thousands of
tonnes of cheap TSP fertilizer containing even more than 100 ppm cadmium
because it was not illegal to do so.
However, there are publications that indicate that during the period
1988-2012 TSP fertilizer bags at different locations in the country
contained 23.5, 30.8, 39.5 and 46.1 ppm cadmium, not withstanding the
SLSI regulations, arousing suspicions that high cadmium containing
phosphate fertilizers may have been imported illegally to Sri Lanka even
up to the recent past.