Abstract:
Heavy metals are the foremost contaminants of food crops especially vegetables,
hence considered a peril to environment. Wastewater irrigation as a substitute to
freshwater has further aggravated the situation by increasing metal load in agricultural
soils and food commodities especially vegetables. Intake of heavy metals via
consumption of contaminated vegetables is notorious for a wide variety of deleterious
health impacts in human population.
In Gujranwala, along with other sources such as tube well and canal water
irrigation, wastewater irrigation in urban and peri-urban areas for the cultivation of
vegetables is a common practice which could be a potential source of metal
contamination. The study area hosts several commercial and industrial centers as well as
support a good amount of agriculture. The current study was therefore carried out is to
evaluate concentration of toxic metals viz Lead, Cadmium, Chromium, Nickle, Mercury
and Arsenic in vegetables (chilli, tomato, onion, spinach, okra, coriander, watermelon,
cauliflower, capsicum and bitter gourd) irrigated with waste water, tubwell water and
canal water in Gujranwala and estimate associated health risk in the inhabitants due to
dietary exposure via consumption of afore mentioned vegetables.
The concentration levels of Pb, Cr, Cd, As and Hg assessed with the aid of atomic
absorption spectrophotometer in vegetables were in range 0.09 - 6.46, 0.00 - 7.69, 0.01 -
4.32, 0.00 - 2.31 and 0.00 - 0.78 mg/kg respectively. Overall trend generated on the basis
mean concentration in vegetables is Pb> Cr > Cd > As > Hg. Hazard Index (HI) values
for cauliflower (2.95), spinach (1.68), onion (1.42), chilli (1.24), watermelon (1.05) and
coriander (1.03) were exceeding 1 for adults, whereas for children HI values for
cauliflower (4.42), spinach (2.59), onion (2.21), chilli (1.78), tomato (1.63), coriander
(1.62), watermelon (1.60) and okra (1.34) were higher the standard indicating potential
non-carcinogenic risk associated with their consumption on a longer run. Results revealed
that children are at higher risk than adults.
Cancer risks associated with Pb, Cr, Cd and As ranged 1.74E-06 - 1.05E-05,
1.13E-04 - 6.40E-04, 1.27E-05 - 2.67E-04 and 0.00E+00 - 9.74E-04 respectively forv
adult consumers. In children risk of cancer was higher for Pb, Cr, Cd and As, ranging
from 3.74E-06 - 2.24E-05, 1.62E-04 - 9.22E-04, 1.83E-05 - 3.85E-04 and 0.00E+00 -
1.40E-03 respectively. It can be concluded that consumers are at low cancer risk due to
consumption of vegetables understudy. However, heavy metals even at low concentration
are not desirable and continuous monitoring on regular basis is a dire need for safe and
health consumption of vegetables as well as to avoid ecological hazards.
