Heavy metal pollution and Human health concern

PollutionRising,ChineseFearforSoilandFood
A farmer worked her land in the shadows of a lead factory in Hengyang, Hunan province, where scholars say soil pollution is especially acute. CreditSim Chi Yin for
The New York Times
The New York Times Dec 30, 2017

Ten major chemicals and elements of public health concern
WHO (2013)

Source: Van Liedekerke et al. (2003)

• Have high densities (>5g/cc)
• Atomic number (>20)
• Toxic in nature
• Non-degradable
• Metalloids (As)

Contamination vs. pollution
• “Contamination” is above or below the
background or threshold level
• “Pollution” means concentration above
threshold
• Pollution levels depend on who (child or
adult), where (soil, water, air), over what
time (8 hrs or chronic), exposure occurs.

@2013, ICE, All rights reserved
What causes heavy metal pollution?
Sediment from solid wasteIndustrial waste
Mining waste

Anthropogenic
sources of heavy
metals in soil
Tannery
BatteryDistillery
Steel Fly ash
Electroplating
Mining
Smelting

Forms of heavy metals in soils
Brady and Weil, 1999

Limits of different heavy metals in sewage sludge
Brady and Weil, 1999 and Labno,2001

Heavy metals in the food chain
Brady and Weil, 1999

CHEMISTRY OF HEAVY METAL POLLUTION
A. As pollution
B.Hg pollution
T.ferroxidans

Mechanism of chromium toxicity in cells

Modern approach
EKRT functioning scheme

July 1, 2020 38
RESEARCH
PAPERS

Impact of heavy metal contamination of
Bellandur lake on soil and cultivated vegetation
Lokeshwari and Chandrappa,(2006)
Objective: To assess the extent of heavy metal contamination
of vegetation due to irrigation with sewage fed lake water on
agricultural land

MATERIALS AND METHODS
19 water samples were collected in polyethene bags at monthly intervals
12 vegetables, fruit, crop, milk, plant samples were collected in polyethylene
bags once in 3 months
8 soil samples (0-15 cm depth) were collected from the same locations of
sampling
Water samples (500 ml) were filtered using Whatman no 41 fiter paper
The filtrate is preserved with 2 ml nitric acid to prevent precipitation
Samples were then concentrated to 10 fold on a water bath and subjected
to nitric acid digestion using micro wave assisted technique at 30 bar
pressure and power at 700 watts.
Sample preparation

Soil samples were air dried and ground into fine powder of1 mm
Well mixed samples of 2 g each were taken in 250 ml glass beaker,digested
with 10 ml aqua regia on a sand bath for 2 hours
After evaporation to near dryness,the samples were dissolved with 10 ml of
2% HNO3,filtered and then diluted to 50 ml with distilled water
Vegetable,fruit,crop and plant samples were washed,cut into pieces,air
dried for 2 days and finally dried at 1000 C for 3 hrs
Samples were ground and passed through 1 mm sieve, digested with 10 ml
HNO3
Well mixed milk samples digested with aqua regia for 3 days on a sand bath
Samples were then filtered and diluted to 50 ml

Analysis was done using AAS (GBC Avanta version)
Power X ray diffraction pattern of the soil sample was done
on Philips Xpert pro X ray diffractometer
Transfer factor (TF) was calculated for each metal according to
the following formula : TF=Ps(ug/g dry wt/St(ug/g dry wt)
where ps is the plant metal content originating from the soil
and st is the total metal content of the soil
The detection limits for Fe,Zn,Cu,Ni,Cr,Pb and Cd were 0.05,
0.008, 0.025, 0.04, 0.05, 0.06, 0.009 mg/l respectively.
Analysis

CONCLUSION
Sewage is the main source of pollution in Bellandur lake.
Use of this sewage water for irrigation purpose has
contaminated the vegetables ,cereals and milk and may
cause a potential threat of heavy metal pollution

Heavy metal contamination of water bodies, soils
and vegetables in peri urban areas of Bangalore city
of India
Varalakshmi and Ganeshamurthy (2012)
Objective: To assess heavy metal contamination of water, soil and
vegetables in the peri-urban areas of Bangalore irrigated with
water of Bellandur, Varthur, Byramangala and Nagavara lakes.

Period of experiment -2005-2008
Site of study- vegetable growing areas near
Bellandur , Varthur , Byramangala and Nagavara
lakes
Uncontaminated control site- A farm away
from these tanks where bore well water was
used for growing vegetables
Soil and vegetables samples (amaranthus, palak,
carrot, radish, tomato and beans) both from
contaminated and uncontaminated sites from
the farmers fields were also collected.
Material and methods

Soil samples were dried at room temperature
and ground to fine powder. Vegetable
samples were dried in oven at 800 C,
powdered and passed through a 2 mm sieve
The soil and vegetable samples were digested
with triacid mixure ( HNO3, HClO4 and H2SO4
in 5:1:1 ratio) (Allen et al. 1986).
The total heavy metal contents in water
samples, digested soil and vegetable samples
were estimated using Perkin Elmer Flame
Atomic Absorption Spectrophotometer.

RESULTS AND DISCUSSION
Cd content in vegetablesPb content in vegetables

Ni content in vegetables Cr content in vegetables

Location Cd Pb Cr Ni
Varthur tank Mean 0.033 0.075 0.289 0.039
n: 36 Std. dev 0.009 0.039 0.289 0.036
Bellandur tank Mean 0.039 0.065 0.291 0.042
n:36 Std. dev 0.008 0.025 0.198 0.033
Byramangala tank Mean 0.022 0.059 0.311 0.04
n:36 Std. dev 0.011 0.024 0.215 0.03
Nagavara tank Mean 0.014 0.039 0.12 0.027
n:24 Std. dev 0.002 0.016 0.067 0.018
Borewell of
Uncontaminated site
Mean 0.002 BDL 0.015 0.0016
n: 12 Std. de 0.0008 - 0.007 0.0008
Safe limit* 0.01 0.5 0.1 0.2
Table 1. Heavy Metal Concentrations (mg/L) In Different Water Bodies of Bangalore.

Location Cd Pb Cr Ni
Near Varthur tank Mean 2.9 68.12 56.5 57.3
n: 36 Stddev 0.7 18.7 14.64 19.9
Near Bellandur tank Mean 2.38 64.9 51.8 45.7
n: 36 Std. dev 0.67 12.5 13.4 14.5
Near Byramangala
tank
Mean 2.06 55.02 92.78 46.1
n: 36 Std. dev 0.71 7.67 14.05 79
Near Nagavara tank Mean 1.92 47.04 35.08 48.2
n: 24 Std. dev 0.25 7.67 7.83 9.09
Uncontaminated field Mean 0.9 39.6 34.2 34.9
n: 12 Std. dev 0.22 7.47 6.31 8
Safe limit* 1.6-3.0 90-300 100-120 48-75
Table 2. Heavy Metal Concentrations (mg/kg) In Soils Receiving Sewage
Water From Different Water Bodies in Bangalore
*Source; Kabata and Pendias (1984) n: number of samples

Conclusion
The waters of 4 major water bodies of Bangalore were contaminated with heavy
metals especially Cd and Cr.
Leafy vegetables accumulated highest concentrations followed by root and
fruit vegetables.
Vegetables grown with waters of Varthur and Bellandur tank accumulated higher
concentrations of Cd, Pb and Ni whereas vegetables grown with waters of
Byramangala tank accumulated very high levels of Cr.

Transfer of metals from soil to vegetables in an
area near a smelter in Nanning, China
Yu-Jing Cui et al.(2004)
Objectives: To investigate the metal contamination in soils and vegetables
To evaluate the possible health risks to local population through food
chain transfer

Site of experiment: Near a smelter in Nanning,
China
Soil order: Udic ferrosols
Production potential of the smelter: 12000 t of
lead and 4000 t of antimony every year
Solid waste generated is dumped in the nearby
arable land.
Villages selected for the study: V1 1500 m away
from smelter
V2 500 m away from the smelter
V3 50 km away from the smelter

Metals
(mg kg -1)
Village 1
(N = 10)a
Village 2
(N= 12)
Village 3
(N=6)
Significance
Cd 0.87 22.06 0.12 P < 0.001
Zn 44.88 596.78 29.7 P < 0.001
Cu 4.01 38.97 10.35 P= 0.018
Fe 9669.21 14,612.41 10,183.06 NSb
Ca 810.22 2906.85 960.73 P < 0.001
Pb 73.67 991.59 16.1 P < 0.001
a Number of samples.
b No significant difference.
Geometric means of metals in arable soils in the three
villages (dry weight)

Metals
(mg kg -1)
Exposed
village (V1)
(N= 32)
Exposed
village (V2)
(N= 33)
Control
village (V3)
(N = 20)
Significance
Cd 0.15 0.24 0.02 P < 0.001
Zn 8.40 11.20 3.70 P < 0.001
Cu 0.48 0.76 0.38 P < 0.001
Fe 20.70 32.30 9.70 P < 0.001
Ca 879.20 1421.90 428.20 P < 0.001
Pb 0.45 3.78 0.03 P < 0.001
Geometric means of metals in edible parts of vegetables in
three study groups (fresh weight basis)

Daily intake of metals (DIM) = daily vegetable
consumption x mean vegetable metal
concentrations (mg/day; fresh weight)where
daily vegetable consumption was based on the
survey for village.
Risk Index = DIM/RfDo, here RfDo represents
safe levels of exposure by oral for lifetime
(USEPA, 2002). An index under 1 is assumed as
safe.
TF = metal concentration in plant tissue (fresh
weight basis)/metal concentration in soil (dry
weight basis) where the plant was grown

Metals Village 1 Village 2 Village 3 Significanc
e
Cd 0.12 0.22 0.02 P < 0.001
Pb 0.30 2.83 0.02 P < 0.001
Zn 4.60 5.81 1.89 P < 0.001
Cu 0.21 0.35 0.22 P < 0.001
Fe 10.05 15.74 8.05 P < 0.001
Ca 402.41 709.43 380.08 P < 0.001
Geometric mean for daily intake of metals (DIM) from soil
through vegetables (mg/day, fresh weight)

Conclusion
Results showed that in
V1 and V2 both soils and vegetables were severely
contaminated
with Cd and Pb.
The following vegetable crops are relatively safer to consume
Ipomoea aquatica Forsk, Vigna sinensis, Allium tuberosum,
Nasturtium officinale (with low Cd accumulation) and Allium
schoenoprasum L., Brassica campestris var. parachinesis and
Benincasa hispida Cogn. (with low Pb accumulation).

An Assessment of Heavy Metal Contamination in
Vegetables Grown in Wastewater-Irrigated Areas of
Titagarh, West Bengal, India
Gupta et al.(2007)
Objective:To Assess Heavy Metal Contamination in irrigation
water and Vegetables Grown in Wastewater-Irrigated Areas of
Titagarh

• Untreated and treated wastewater Samples
• Top-soil (0–15 cm depths) and
• Nine vegetable samples were analyzed
• 50 ml of wastewater samples digested
with 10 ml concentrated HNO3 at 800C
(APHA 1985)
Soil samples were air-dried, crushed
and passed through 2-mm mesh sieve
and stored at ambient temperature
prior to analysis
Material and Methods
Sample preparation

• Digested samples of water, soil and
vegetables were filtered through the
Whatsman No.42 filter paper and diluted to
50 ml with distilled water.
• Heavy metal concentrations of wastewater, soil
and vegetable samples were estimated by
Atomic Absorption Spectrometer (Perkin
Elmeyer Analyst 400).
• Freshly harvested mature vegetables were
washed with distilled water ,cut into small
pieces, dried in oven at 700C for 48 h and then
ground to powder
•0.5 g each of soil and vegetable samples were
digested (wet acid digestion) until the solution
became transparent.

The concentration of Ni in the present
study was highest in Spinach (69.22
mg/kg) followed by Radish (62.70 mg/kg),
which were 46 and 41 times higher than
the PFA limit
The results indicate that wastewater-
irrigated vegetables accumulate heavy
metals beyond prescribed toxic limits and
may cause serious health hazards to
people who consume these vegetable
products regularly.
Conclusion

Arsenic Contamination in Rice, Wheat, Pulses, and
Vegetables: A Study in an Arsenic Affected Area of West
Bengal, India
Bhattacharya et al. (2010)
Objectives: To find the distribution of arsenic in irrigation water, soil, and crops
and to assess the influence of arsenic contaminated irrigation water and soil on
rice, pulses, and vegetables cultivated in the arsenic affected five blocks of Nadia
district, West Bengal. To evaluate the severity of human health risk from arsenic
toxicity through water–soil–plant system.

Material and Methods
Five blocks of Nadia district (Haringhata, Chakdaha, Ranaghat-I, Shantipur, and
Krishnanagar)
Sample Collection
Five sub-samples of Boro rice, wheat, different oil seeds, and vegetables like cabbage,
cauliflower, brinjal, potato, etc were collected
Ground water samples have been collected from the shallow tube well pumps of large
diameters, used for irrigation in the study area
Sample Treatment
Same treatment for soil, irrigation water and different crops was done with the
standard methods
Study Area
Sample Analysis
The total arsenic of samples was analyzed by flow injection hydride generation atomic
absorption spectrophotometer (FI-HG-AAS), Perkin Elmer Analyst 400 using external
calibration (Welsch et al. 1990).

Results and Discussion
Arsenic concentrations in irrigation water samples (n=58)

Arsenic concentrations in soil
samples (n=58)

Correlation between arsenic concentration in irrigation water and in soil samples

The potential of arsenic contamination is very high in
the groundwater of the study area which is enhancing
the human health risk from arsenic toxicity via water–
soil–plant system .
Even though the study does not indicate an
immediate danger, but the uptake of arsenic by
agricultural plants should be monitored periodically .
Conclusion

Summary
Sewage is the main source of pollution in different lakes of
Bangalore. Untreated sewage water can lead to heavy metal
pollution in humans through water and food.
The order of contamination for different heavy metals was
leafy vegetables >root crops>fruits. Spinach was found to be
a hyper-accumulator of many heavy metals.
It was observed that wastewater-irrigated vegetables
accumulate heavy metals beyond prescribed toxic limits and
may cause serious health hazards to people who consume
these vegetable products regularly

Summary
Crops with low transfer factors from soil to vegetables should be selected in
heavy metal contaminated areas to prevent their bio accumulation
Over exploitation of ground water should be prevented in areas where the potential
of arsenic contamination is very high to reduce the human health risk from arsenic
toxicity via water–soil–plant system
Sewage and sludge as well as different phosphatic fertilizer sources should be
examined for their heavy metal content before application in agricultural fields.

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