Harmful heavy metals found in commonly consumed rice varieties: Study

A recent study has revealed alarming findings regarding the presence of heavy metals in rice, a dietary staple in this country. Arsenic and lead have been detected in harmful quantities in various rice samples, posing significant risks to health.

Regular consumption of these heavy metals through food can lead to severe health issues, including cancer, hypertension, cardiovascular diseases, diabetes, inhibition of haemoglobin synthesis, urinary dysfunction, chronic damage to the gastrointestinal tract, and urinary tract infections.

Led by Dr Nazma Shaheen, professor at the Institute of Nutrition and Food Science, University of Dhaka, a team of researchers conducted the study, "Carcinogenic and non-carcinogenic health hazards of potentially toxic elements in commonly consumed rice cultivars in Dhaka city, Bangladesh". 

Published in the peer-reviewed open access journal "Plos One" on 14 May, the study collected samples of 10 commonly consumed rice varieties from four wholesale markets in Dhaka city. These varieties include Naigarsail, Minikit, Pajam, Katari, Basmati, Kaligira, Chinigura, BRRI-32, Bashful, and Lalbiroi.

Analysis of these rice samples revealed the presence of heavy metals and toxic elements such as arsenic, lead, chromium, copper, cadmium, zinc, manganese, mercury, and nickel in harmful quantities. 

The study also highlighted the carcinogenic and non-carcinogenic health hazards associated with these heavy metals in the human body.

According to the researchers, the allowable limit for lead set by the United States Environmental Protection Agency (USEPA) is 0.000001 mg/kg. However, the research found lead levels in rice ranging from a minimum of 0.01 mg/kg to a maximum of 1.08 mg/kg. Similarly, the level of arsenic was between 0.04-0.35 mg/kg, significantly higher than the allowable limit.

Dr Lelin Choudhury, a public health expert and chairman of Health and Hope Hospital, told TBS that heavy metals like lead can cause diseases, including cancer. The amount of heavy metals a person ingests greatly affects his or her health. Prolonged exposure can lead to cancer, but it can also occur in a shorter time in some cases.

He added that heavy metal intake is especially harmful to children and pregnant women, leading to severe health problems. Therefore, it is crucial to prevent heavy metals from entering our food.

Dr Nazma Shaheen told TBS, "The levels of lead and arsenic in rice exceed safe limits. Long-term consumption can increase the risk of cancer."

She added, "Our research aims to inform the government so measures can be taken to prevent heavy metal contamination in food."

Researchers say arsenic contamination usually comes from groundwater, while lead contamination is mostly caused by human activities and can spread through soil, water, air, fertilisers, and pesticides.

Towhid Hasan, an assistant professor in the Department of Food Technology and Nutrition Sciences at Noakhali Science and Technology University, emphasising the urgent need for awareness, called for action to mitigate health risks associated with heavy metal contamination in rice.

The research paper elaborated on heavy metal health risks, focusing on their effects on human health and the environment.

Arsenic is a widespread environmental toxin linked to skin, lung, and bladder cancer. Chronic exposure can cause skin issues, hypertension, cardiovascular diseases, and diabetes.

Lead is absorbed through food, water, and air. Lead poisoning can inhibit haemoglobin synthesis, damage the urinary, reproductive, and cardiovascular systems, and harm the gastrointestinal tract. In children, lead exposure can impair brain development and reduce intelligence.

Cadmium is a naturally occurring but highly toxic element, primarily absorbed through food. Long-term exposure to cadmium can lead to kidney problems, bone defects, osteoporosis, fractures, and high blood pressure.