Copyright infringement not intended

Picture Courtesy: The Hindu

Context:

A recent study published in the Proceedings of the National Academy of Sciences (PNAS) has revealed that the microbial composition of rice paddies—not just the amount of arsenic in soil—plays a decisive role in arsenic toxicity and yield loss in rice. The research suggests that managing soil microbes could be key to ensuring rice productivity and food safety.

Current status:

Global: Around 150 million people are exposed to arsenic-contaminated rice worldwide. Arsenic toxicity can cause up to 70% yield loss in severely affected fields due to straight head disease. (Source: WHO, FAO, PNAS 2025)

India: India is the 2nd largest rice producer, with 45 million hectares under cultivation.

• High-risk states: West Bengal, Bihar, Assam, and Uttar Pradesh, where groundwater arsenic exceeds 05 mg/L (WHO limit: 0.01 mg/L).
• Rice grains in these areas contain 2–0.4 mg/kg arsenic, reducing yield by 15–40%. (Source: ICAR-NRRI, CGWB 2024)

Developing Linkages:

• In a field study in West Bengal, rice grain arsenic ranged from 4 to 1.68 mg kg⁻¹ dry weight (dw), and arsenic uptake varied by genotype (roots showed 29-167 mg kg⁻¹ dw; translocation factor 4-45%). (Source: PubMed) 

• In a study in eastern Uttar Pradesh on genotype “Shatabdi”, imposing a deficit‐irrigation regime reduced grain arsenic by 6-25% while yield declined only by about 0.9% compared to standard practice. (Source: ijarasem.com) 

• An intervention study in West Bengal found that applying alternate watering‐drying (AWD) irrigation reduced arsenic bioavailability by up to 26%, and the associated practice resulted in 6-8% higher profit (implying better yield or value) compared to continuous flooding in the region. (Source: Millennium Post)

These findings indicate that in India:

• Elevated arsenic in paddy soils/irrigation water is linked to higher arsenic uptake in rice. 

• Even relatively small yield impacts (≈1%) can be detected when arsenic is mitigated by irrigation practice changes. 

• The yield loss specifically attributed to arsenic accumulation (rather than general agronomic factors) is less well-quantified in Indian literature, but interventions show yield can be preserved or improved when arsenic uptake is reduced. 

Implications of Arsenic in Soil:

• Agricultural Impact: Arsenic toxicity reduces rice yield by 15–70%, depending on soil type and microbial imbalance. In West Bengal and Bihar, rice grains contain 2–0.4 mg/kg arsenic, leading to reduced grain filling and straighthead disease. Global yield loss due to arsenic contamination is estimated at 1.4–4.9 million tons annually. (Sources: PNAS 2025; ICAR-NRRI 2024; PMC 2017)

• Food Security & Nutrition: Rice contributes ~40% of caloric intake in India; contamination directly threatens dietary safety. Long-term arsenic exposure in rice-eating populations increases health risks, especially among rural poor in Bengal Basin. (Sources: WHO 2024; FAO 2024) 

• Human Health Implications: Chronic exposure to arsenic-contaminated rice linked to skin lesions, cancer, cardiovascular diseases, and cognitive decline. Around 150 million people globally are at risk from arsenic-contaminated rice consumption. (Sources: WHO 2024; The Lancet 2023) 

• Environmental and Ecological Impact: Arsenic disrupts soil microbial balance, increasing methylating bacteria that form toxic organic arsenic species (DMA, DMMTA). These compounds accumulate in rice and persist in soil–water systems, worsening toxicity over time. (Source: PNAS 2025) 

• Economic Implication: Estimated annual economic loss from arsenic-induced yield decline in South and Southeast Asia exceeds $3 billion. Farmers in arsenic-affected districts face reduced income due to poor grain quality and export restrictions. (Sources: FAO 2024; World Bank 2023) 

Government measures:

• At present, the Food Safety and Standards Authority of India (FSSAI) does not have a specific standard for arsenic in rice; thus, Indian rice is governed by more generic food safety rules. (Sources: Down To Earth) 

• The central government has identified that the states of West Bengal and Bihar are most impacted by arsenic contamination and has suggested adaptive cropping and monitoring measures. (Sources: Business Standard) 

• A regional initiative in West Bengal created an “arsenic-free rice” variety under state agriculture research. (Sources: Telegraph India 

Country wise Comparison:

Way Forward:

• Adopt Arsenic Standards: India lacks a rice-specific limit; adopt 2 mg/kg as per FAO–WHO Codex (2024). 

• Smart Irrigation (AWD): Alternate Wetting & Drying cuts arsenic uptake by ≈26% without yield loss. (Source: ICAR–NRRI 2024) 

• Soil & Microbial Management: Mid-season drainage and silicon fertiliser reduce toxic microbial activity and uptake. (Source: PNAS 2025) 

• Low-Arsenic Varieties: ICAR-developed cultivars show 20–40% less grain arsenic. (Source: ICAR–NRRI 2024) 

• Safe Water Use: Shift from arsenic-rich groundwater (>0.05 mg/L) to surface/rainwater sources. (Source: CGWB 2024; WHO 2024) 

Source: The Hindu