Thursday, June 8, 2023

Vegetables and grains produced in wastewater-irrigated areas of Bhadohi contain a high levels of heavy metals: Research

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Vegetables and grains produced in wastewater-irrigated areas of Bhadohi contain a high level of heavy metals: Research


A study conducted by the researchers of Banaras Hindu University, has shown that vegetables and grains frequently irrigated with mixed wastewater from industrial and residential areas of Bhadohi had higher concentrations of heavy metals (cadmium, nickel, chromium, copper, and zinc) than those irrigated with groundwater. Heavy metal contamination of the food chain is a threat for both food safety and human health. The study was conducted by Prince Kumar Singh, Jay Shankar Yadav, Indrajeet Kumar, and Umesh Kumar under the supervision of Dr. Rajesh Kumar Sharma, Assistant Professor, Department of Botany, Banaras Hindu University from March 2019 to February 2020 in suburban areas of Bhadohi, Uttar Pradesh. The recent findings have been published in a globally reputed journal, TOXICOLOGY REPORTS.

The use of wastewater in agriculture has both positive and negative aspects. As a positive perspective, wastewater is a rich source of nutrients, organic matter, etc. and as a negative perspective, it also contains many harmful toxic metals, micro-organisms, emerging contaminants, etc. The presence of heavy metals in the ecosystem in excess or over the prescribed limits is harmful to flora, fauna, and human health, as well as it becomes the main cause of metallic pollution of wastewater/ irrigation water, soil, and major crops i.e. cereals, vegetables cultivated in suburban areas of developing cities.

In this research work, 84 composite samples of vegetables (palak, radish, garlic, cabbage and brinjal) and cereals (paddy, wheat) were collected from March 2019-February 2020 on seasonal basis. All the samples were washed with running tap water, chopped into small pieces and dried in oven. The dried samples were then ground and made into powder and heated with di-acid (nitric acid and perchloric acid) for 6-8 hours at a constant temperature. The contamination levels of heavy metals (cadmium, nickel, chromium, copper, and zinc) in the filtrates of vegetables and grains were analyzed by Atomic Absorption Spectrophotometer (Perkin-Elmer AAnalyst 800, USA).

Concentrations of different heavy metals in vegetables and grains from wastewater and ground water irrigated areas of Bhadohi are given in Table 1. The maximum and minimum amount of copper was found in wheat grains (27.9 mg/kg) and garlic (7.1 mg/ kg), respectively. The highest amount of nickel and chromium was also found in wheat (42.3 mg/kg and 17.1 mg/kg, respectively) and the lowest in brinjal and garlic (10.3 mg/kg and 2.9 mg/kg, respectively). The highest concentrations of zinc and cadmium was found in palak (58.4 mg/kg and 5.3 mg/kg, respectively) and the lowest in garlic (27.6 mg/kg and 1.9 mg/kg, respectively). Copper and chromium were found below the safety limit of Indian Standard in all vegetables and grains.

Zinc exceeds the safety limit only in palak among the tested vegetables and grains. Nickel and cadmium exceeded the safety limits of both Indian and WHO/FAO standards in all the tested vegetables and grains. Nickel concentration in groundwater irrigated vegetables and grains were also found above the safety limits of Indian standard. The maximum daily intake of heavy metals by the local residents was recorded for nickel (0.288 μg g-1day-1 by the children) through consumption of wheat grains and minimum for chromium (0.001 μg g-1day-1 by an adult) via consumption of radish and garlic. The health index of copper, nickel, and cadmium was more than a unit for children and adults consuming wheat and paddy grains. If such contaminated food items are consumed for the long term, these heavy metals i.e. copper, nickel and, cadmium can pose health risk to local people. Thus proper monitoring and management of these metals are required.

Continuous consumption of heavy metal contaminated vegetables and other food items can cause different types of diseases such as mental and behavioural disorders, asthma, cancer, nervous system-related diseases, cardiovascular diseases (heart-related), kidney or renal-related diseases, irregularities in the endocrine system especially in pregnant women (mother and child), obesity, breast cancer. In particular, inadequate sanitation facilities, poor septage management, and lack of policies for sewage and sanitation can be attributed to excessive sewerage. Ground water is getting contaminated on a large scale due to industrial waste and unviable agricultural practices.

In developing countries, the creation of infrastructure to collect and treat wastewater requires further strengthening of financial resources. This is especially the case for advanced treatment technologies, which can be costly, although solutions to this problem include using groundwater instead of wastewater for irrigation, avoiding mono-cropping, use of various scientific methods, etc. This problem can be avoided to a large extent by using such methods. Whether this type of water can be used for irrigation or not, the farmers should keep taking the advice of the concerned scientists from time to time. Scientists should also enhance their knowledge in this perspective through training and meetings from time to time.

Table 1: Mean concentrations of heavy metals in vegetables and grains from wastewater irrigated areas of Bhadohi, Uttar Pradesh, India

Vegetable/grainsConcentrations of heavy metals (mg kg-1)
Palak12.4 (4.2)20.9 (3.0)58.4 (6.6)5.3 (0.5)6.2 (2.1)
Radish10.4 (3.7)20.9 (2.8)36.8 (6.0)3.4 (0.5)3.4 (1.3)
Garlic7.1 (3.3)14.7 (3.0)27.6 (5.8)1.9 (0.4)2.9 (1.3)
Cabbage13.9 (3.6)32.4 (4.0)40.5 (5.6)3.3 (0.7)4.4 (2.5)
Brinjal11.5 (3.8)10.3 (3.3)51.6 (4.8)3.5 (0.6)5.5 (1.8)
Rice grains23.3 (6.1)37.1 (5.3)36.1 (7.8)3.1 (0.6)12.8 (2.0)
Wheat grains27.9 (5.5)42.3 (4.5)40.5 (9.0)3.1 (0.6)17.1 (2.7)
Average values15.2 (4.3)25.8 (3.7)41.6 (6.5)3.4 (0.6)7.4 (2.0)
Safety limita30.01.550.01.520.0
Safety limitb40. 

Values given in parenthesis are for ground water irrigated vegetables and grains.

aIndian standard (Awashthi, 2000)

bWHO/FAO standard (WHO/FAO (2007)

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