An Assessment of Heavy Metal Contamination of Rice Varieties Produced Across India States with a Lens of Rising Cancer Burden.

INTRODUCTION
Rice is a staple food for more than half of the world’s population, a key source of energy and nutrients. However, it readily absorbs environmental toxins such as inorganic arsenic (iAs) a group 1 and lead (iPb) a group 2A carcinogen through irrigation water and soil, posing serious health risks.[12] Ingestion of arsenic and lead contaminated rice is associated with cancer of lungs, stomach, urinary bladder, kidney, brain, liver, skin, and breast and other adverse health conditions.[345] The Food Safety and Standards Regulations (FSSAI), 2020, caps the permissible limit at 0.2 mg/kg for lead and 0.4 mg/kg for arsenic in polished rice.[6] However, these studies from South and Southeast Asia have reported toxic contamination of rice across regions.[78] In India, the issue is particularly grave as disparate areas and industrial zones showing heavy concentrations of arsenic and lead in soil and water.[910]
Cancer is a major public health problem with 19.3 million new cases and 10 million deaths reported in GLOBOCAN 2020.[11] India reported 1.46 million new cancer cases the same year with breast, lungs, colorectal, and oral cancers linked to environmental exposures.[12] Arsenic in rice is a key concern given a median cancer risk of 3 per 10,000 people, rising to 2.8% in Indian population.[1314] Despite being one of the largest producers and consumers of rice, India faces huge challenges in ensuring food standards and safety of rice crop arising out of industrial pollution, contaminated irrigation sources, and adverse soil conditions.[1516]

MATERIALS AND METHODS

Study area and sample collection
A cross-sectional study was conducted across six major rice-producing states of India viz Punjab, Uttar Pradesh, Madhya Pradesh, Andhra Pradesh, Telangana, and Maharashtra spanning both northern and southern regions. Thirteen districts were randomly selected, and rice samples were collected over 6 months from local markets, traders, and rice mills to ensure correlatability and sample diversity. Each 200 grams sample was sealed in sterile, airtight poly packets and labeled variety, source, and collection date.
Samples were subsequently transported to a central storage facility in Gurugram, in standard conditions later sent to accredited food laboratory results for analysis. Epidemiological data on cancer incidence from the selected states were gathered through desk review of cancer registry reports and published documents to explore possible ecological links.

Sample processing and storage
Rice samples were manually cleaned and stored at 15-20°C in sealed pouches until laboratory analysis. Spoiled or infested samples were discarded to avoid measurement errors.

Analytical methods and regulatory limits
Arsenic and lead concentrations in rice samples were determined using Indian Standard (IS) methodologies:

Arsenic (As): IS: 11124:1984, using atomic absorption spectrometry (AAS) for trace metal detection.

Lead (Pb): IS: 12074:1987, which uses graphite furnace atomic absorption spectrometry (GFAAS) for precise quantification.

The laboratory analysis was conducted at two separate facilities, i.e. Shri Ram Institute for Industrial Research, Gurgaon, and Equinox Labs, Zirakpur, both accredited facilities adhering to standardized testing protocols. The Codex Alimentarius Commission (CAC) sets arsenic limit in rice at 0.2 ppm,[17] while the FSSAI permits up to 1.1 ppm in polished rice.[18] For lead, codex allows 0.2 ppm in cereals, although WHO stresses on no safe exposure level due to its cumulative toxicity and recommends minimizing intake from all sources.[19]

Data analysis
Descriptive statistics were used to report arsenic and lead levels against FSSAI and WHO limits to gauge contamination patterns. This study used an ecological design, using aggregated environmental and publicly available health data at the population level.

RESULTS
A total of 19 rice samples from 5 Indian states were analyzed across various rice varieties [Figure 1]. Punjab, Telangana, and Uttar Pradesh exhibited significantly elevated levels of arsenic and lead. Maharashtra reported the highest mean arsenic concentration of 3.14 ppm, exceeding FSSAI and WHO limits, while Madhya Pradesh had the highest mean lead level of 3.63 ppm, and a maximum observed level reaching 5.79 ppm.
The arsenic concentration ranged from 1.07 ppm (BPT, Madhya Pradesh) to 3.90 ppm (Sona Masori, Telangana) with a mean of 2.39 ± 0.86 ppm, exceeding FSSAI’s limit of 1.1 ppm. The highest concentrations were in Sona Masori (Telangana) and Basmati (Punjab). Of total, 89.5% of samples exceeded the FSSAI limit, with Punjab and Telangana varieties showing higher arsenic concentrations.
Lead concentration ranged from 0.54 ppm (Basmati, Punjab) to 6.44 ppm (Sona Masori, Telangana) with a mean of 2.99 ± 1.76 ppm, much above the WHO limit of 0.2 ppm. All samples exceeded the WHO’s safe limit for lead, indicating severe contamination. The highest levels were found in Sona Masori of Telangana (6.44 ppm) and Nizamabad (5.45 ppm). While Punjab and Maharashtra had lower lead levels, arsenic remained notable. A strong arsenic–lead correlation in Telangana points to contaminated water or soil as possible sources [Table 1].

Cancer burden
On literature review, it was observed that the state of Uttar Pradesh, Maharashtra, and Madhya Pradesh exhibits significant cancer burden, with a high prevalence of incriminated lung, stomach, and gastrointestinal cancers. Uttar Pradesh, Maharashtra, and Madhya Pradesh account for approximately 14.4%, 8.3%, and 5.6% of cancer-related deaths, while of deaths nationwide.[20]
The highest sample average arsenic levels were observed in Maharashtra (3.14 ppm) and Uttar Pradesh (3.12 ppm). Punjab (2.83 ppm) and Telangana (1.99 ppm) also exhibited arsenic concentrations well above the FSSAI limit of 1.1 ppm. The lowest arsenic concentration was found in Madhya Pradesh (1.73 ppm), although still exceeding safe limits. The highest average lead contamination was found in Uttar Pradesh (4.55 ppm), Punjab (4.48 ppm), and Madhya Pradesh (3.63 ppm). Telangana (3.12 ppm) also exhibited high lead levels, far exceeding the WHO limit of 0.2 ppm. Maharashtra had the lowest average lead contamination (1.40 ppm), although still seven times the WHO limit [Table 2].

DISCUSSION
In this study, all rice samples had excessive arsenic and lead levels above the recommended WHO and FSSAI thresholds, posing potential health risks. The findings indicate significant heavy metal contamination across rice varieties and different regions of India, particularly in the states of Telangana and Madhya Pradesh.
Heavy metal contamination in rice is a critical global issue, with arsenic and lead being the most concerning contaminants due to their established health risks. Variations in contamination levels across different geographical regions indicate that the extent of exposure is highly dependent on environmental, regulatory, and anthropogenic factors.[1416] South Asian countries such as India, Bangladesh, and China report some of the highest arsenic and lead concentrations in rice, primarily due to groundwater contamination and industrial emissions.[21] By contrast, regions such as Japan, the United States, and Europe have significantly lower levels due to strict environmental regulations and controlled agricultural practices. A comparative study found that arsenic levels in Bangladeshi rice ranged from 0.5–0.8 µg/g, whereas Indian rice samples exceeded 1 µg/g in arsenic-affected regions.[8] Similarly, lead contamination was significantly higher in industrialized areas of India and Bangladesh, reaching values as high as 3 µg/g, well above the WHO permissible limit of 0.2 µg/g.[22] These findings reinforce the need for region-specific mitigation strategies to reduce heavy metal accumulation in rice.
Arsenic is a classified carcinogen linked to the cancer of the lung, bladder, liver, and skin.[23] Studies from India’s arsenic-affected regions, such as West Bengal and Bihar, confirm that chronic exposure through rice significantly increases risk of malignancy.[24] Lead, although primarily recognized for its neurotoxic effects, has also been associated with genotoxicity and potential carcinogenicity.[25] Long-term exposure to these metals leads to oxidative stress and DNA damage, increasing the likelihood of malignant transformation.[26] This study’s findings are consistent with global reports indicating that rice consumption contributes substantially to arsenic-induced cancer risks.[9] In addition, research in Iran and Saudi Arabia has raised concerns over imported rice containing arsenic and lead within legal limits but still posing long-term health risks.[2227] Significant geographical disparities in arsenic and lead contamination in rice noted across India. High arsenic toxicity in West Bengal, Bihar, Assam, Jharkhand, Chhattisgarh, and Uttar Pradesh is widespread due to irrigation with contaminated water. Similarly, lead contamination in rice has been linked to industrial pollution and wastewater irrigation, particularly in Punjab, Ludhiana, and other industrialized zones.[28] A multiregional study on arsenic uptake in different rice cultivars further highlighted variability in contamination, emphasizing the need for targeted food safety monitoring in high-risk rice-producing areas.[8] Globally, the arsenic and lead contamination levels observed in Indian rice are comparable with those reported in Bangladesh, China, and Iran.[729] Despite existing regulatory frameworks, FSSAI and WHO guidelines arsenic and lead contamination in rice remains a pressing public health concern in India. Effective mitigation strategies such as alternative irrigation sources, soil amendments, and selective breeding of rice varieties with lower heavy metal uptake should be prioritized.[3031] A study conducted in Bangladesh and Vietnam demonstrated safe irrigation practices significantly reduced arsenic accumulation in rice.[32] Moreover, exploring food fortification and processing techniques to minimize arsenic and lead bioavailability warrants further investigation with longitudinal studies assessing the health impacts.
Numerous studies confirm that arsenic contamination in rice is primarily linked to groundwater irrigation, especially in regions such as West Bengal and Bihar, where arsenic levels in water exceed safety limits.[91625] Lead contamination is strongly associated with industrial pollution and soil contamination from atmospheric deposition and high urbanization. The findings of this study underscore the urgent need for regulatory intervention and continuous monitoring of heavy metal contamination in rice. Strengthened food safety policies, cross-border collaboration on agricultural practices, and enhanced consumer awareness initiatives are critical for mitigating contamination risks at both national and global levels.

Study limitations
This study provides valuable insights into arsenic and lead contamination in Indian rice varieties; however, it had certain limitations.

Sample Size and Geographical Coverage: A larger data set across more diverse agroclimatic zones would provide a more comprehensive contamination profile.

Bioavailability and Health Risk Estimation: The study did not assess bioavailable fractions or individual dietary intake variations.

Confounding Factors and Genetic Susceptibility: This study did not factor confounding variables, i.e., genetic susceptibility, cooking methods, and coexposures.

Ecological study: The ecological study suggests group level disease variation, it cannot confirm disease causation relationship, and the results cannot be applied to individuals.

Recommendations
Implementing safe irrigation techniques such as Alternate Wetting and Drying (AWD) can significantly reduce arsenic uptake in rice, making it a viable strategy for India.[32] In addition, biochar soil amendments have shown promise in lowering arsenic bioavailability, while selective breeding and genetic introgression can help develop low-uptake rice cultivars for contamination-prone regions. To protect consumers, public health campaigns should promote effective mitigation techniques such as washing, parboiling, and cooking methods to reduce arsenic exposure. Mandatory labeling of rice from high-risk areas would also enable informed consumer choices. Future research should focus on longitudinal epidemiological studies assessing the cancer risk linked to chronic heavy metal exposure with collaboration of policymakers, agricultural scientists, and healthcare experts.

CONCLUSION
This study highlights significant arsenic and lead contamination in Indian rice, highlighting urgent public health and regulatory action. More than 90% of samples exceeded the safety limits underscoring need for urgent and effective interventions to reduce contamination.[303132] A multidisciplinary approach involving routine monitoring, soil remediation, and AI-driven surveillance, along with longitudinal health studies, is essential to inform policy and support sustainable rice production.

Conflicts of interest
There are no conflicts of interest.