Abstract
A study was conducted to assess the heavy metal exposure through diet in different socio-economic groups of Dhaka
and Mymensingh cities in order to determine the probable health risks. At first, two separate survey works were
conducted during summer and winter to evaluate the dietary pattern in the two locations which revealed that the diet in
all income groups from both cities were carbohydrate dominated. The other major food categories evaluated were animal
proteins, pulses, vegetables, spices and oils. Seasonal and socioeconomic variations in dietary pattern of inhabitants of
both locations were there. Overall, low income level (LIL) and mid income level (MIL) groups consume significantly
higher amount of carbohydrates than high income level (HIL) group and carbohydrate consumption was higher in
Mymensingh by all income groups than Dhaka. Food categories having significant variations among different income
groups included animal proteins, pulses, spices and oils which were higher among HIL. Among the vegetables, nonleafy vegetable consumption during winter was greatly increased in all income groups and both locations. Among the
heavy metals contents of Cu and Fe were higher in both rice and wheat in samples from Dhaka. Whereas, Zn, Mn, and
Cr concentrations were higher in both rice and wheat samples from Mymensingh. The contents of Ni, Pb and As were
higher in rice samples of Mymensingh. Among the pulses, the contents of Zn and Fe in both lentil and mungbean were
higher in Dhaka and Mn, Cd, Cr and Pb were higher in Mymensingh. Copper and Ni contents in lentil from Mymensingh,
and Cu and Ni contents in mungbean from Dhaka were higher. Among the spices, the contents of Cu, Cd and As in
green chili were higher in Dhaka and Zn, Fe, Mn, Cr and Pb were higher in Mymensingh. In general, the heavy metal
load in the selected items analysed were comparatively higher in Mymensingh. Among all the cereal and pulse samples,
a number of samples from both locations exceeded maximum permissible level (MPL) of Pb and As. In Dhaka, the
contents of heavy metals in a number of winter vegetables like brinjal, bottle gourd, cucumber, tomato and potato and
in summer vegetables like bitter gourd, cucumber, snake gourd, potato, taro, etc. exceeded the MPL values, notably,
for As and Pb. In Mymensingh, the content of Pb in most of the summer vegetables exceeded MPL value; a number of
other summer (brinjal, potato, taro) and winter (brinjal, papaya, potato) vegetables exceeded the MPL values for As and
Cd. Among fish, dry fish and broiler chicken samples Pb contamination was beyond the MPL level, and tilapia and koi
fish had greater level of contamination. Dietary intake of different metals varied with season, location and income groups.
In general, average daily intake of most metals were higher during winter season with the exception of Pb. Daily intakes
of Fe, Cu and Cd were higher in Dhaka while that of Mn, Ni, Cr, Pb and As were higher in Mymensingh. The average
daily intakes of Mn (in Mymensingh) and Cu (in Dhaka) exceeded the upper limits by most income groups. As a whole,
Cd, Cr, Pb and As intake were slightly higher in low and mid income groups of population. The health risk assessment
results showed that incremental lifetime cancer risk (ILCR) from As and Cd exposures among different income groups
were of concern. Cancer risk from As exposure were more evident in different income groups of Mymensingh and the
main exposure sources were cereals and animal proteins. While in Dhaka, the critical exposure source was non-leafy
vegetables. Cancer risk from Cd was of concern in both cities, however, higher among all income groups of Dhaka.
Cereals were the principal critical food source for Cd. The cumulative cancer risk was higher in Dhaka and the critical
food categories were cereals, animal proteins and non-leafy vegetables. The non-cancer risks in terms of hazard index
was higher in Mymensingh than in Dhaka city; and lower income groups were more vulnerable to such risks. The main
reason behind this was the intake of high volume of carbohydrates in the diet of low income group of people as itappeared the most significant rout of heavy metal intake.