Climate Change And The Rising Threat Of Arsenic In Rice – Analysis

Rice farmer in Kerala, India.

 July 23, 2025 

By Observer Research Foundation

By Shoba Suri and Tanya Verma

According to recent reports, arsenic has been detected in all samples of rice in the United States (US), with over a quarter exceeding the Food and Drug Administration (FDA) food safety guidelines. Thus, it becomes imperative to mention that climate change is impacting not only weather patterns and agricultural productivity, but also aggravating the invisible hazards in food systems.

One of these threats that remains inconspicuous is the increasing incidence of inorganic arsenic in rice—especially in the context of India, where rice is a dietary staple. The carbon dioxide levels in the air are increasing, and temperatures are climbing, which, in turn, is affecting how crops interact with soil and water. Moreover, it is also affecting the redistribution of nutrients and toxins of crops. Nonetheless, lately arsenic contamination in rice, which has always been closely linked to geography and groundwater exposure, is translating into a climate-related issue impacting both food safety and people’s      health.

The issue is further compounded by prevailing rice cultivation practices. Mostly cultivated during floods within flooded paddies, rice grows well in low-oxygen conditions that unintentionally enhance the bioavailability of arsenic. Such predispositions—along with the widespread use of irrigational water contaminated by arsenic—make it possible to transform toxin into soluble form, which is easily absorbed by the rice roots.

This is further exacerbated by climate change, which induces modifications in the soil chemistry, temperature, and water balance. This results in climatic conditions that have hastened the uptake of arsenic. In India, the problem is exacerbated because flood irrigation is extensively used in areas where arsenic is prevalent. With rising temperatures, the mean consumption of inorganic arsenic in India periodically (now estimated to be 1.54 micrograms in one kilogram of body weight) is expected to increase to 2.21 micrograms. The increase poses a risk to vulnerable groups and communities that routinely consume rice in their meals.

Inorganic arsenic is highly toxic and naturally present in soil and ground water. This can enter the human body through the consumption of crops such as rice, which is absorbed in waterlogged areas. Prolonged exposures to low doses are linked with high risks of skin, lung and bladder cancer, cardiovascular diseases, and developmental problems in children. The Environmental Protection Agency has recently re-evaluatedthe carcinogenicity of arsenic, pegging it even higher and warranting an urgent intervention.

The World Health Organization (WHO) does not set a certain limit of arsenic in rice. Still, the Codex Alimentarius Commission, a United Nations (UN) body, jointly administrated by WHO and Food and Agricultural Organization (FAO), has set a ceiling of 0.2 mg/kg (or 200 0g/kg) of inorganic arsenic in polished rice, yet in a majority of the regions this limit is exceeded. Asia is particularly affected by elevated arsenic in rice in countries such as Bangladesh, China, India, Vietnam, Myanmar, and Indonesia. According to a study published in Lancet Planetary Health (2024), the climatic effect of arsenic contamination in rice is projected to increase lifetime cancer cases (from 13.4 to 19.3 million in China) and non-communicable diseases in Asian countries, including India, by 2050. 

This threat is not uniform across Indian states. It persists most severely in southern Indian states of Andhra Pradesh, Telangana, Karnataka, Tamil Nadu, and Kerala, where rice predominates the cereal basket, making them vulnerable due to high consumption of 60-90  percent and flood irrigation practices in areas where arsenic is predominantly found. 

The growing crisis calls for a concerted multi-faceted response. At the farm level, it includes selecting low-arsenic rice varieties using alternate wetting and drying irrigation methods instead of continuous flooding, and amending soil with silicon or iron to reduce arsenic bioavailability. Additionally, regulatory reforms must accompany such practices to ensure a more inclusive redressal. Unlike the European Union(EU) and the United States (US), where limits have been set on arsenic levels in infant rice cereals and baby food, India lacks binding regulatory standards for arsenic levels in rice. 

Display of quality markers – such as arsenic level should be clearly listed by retail stores through easily understandable and accessible Certificates of Analysis (COAs) from recognised laboratories. Such COAs can be digitally distributed to packaging through QR codes, enabling consumers to make informed choices. Furthermore, governments can promote affordable and user-friendly arsenic test kits to ensure safety.

Additionally, decentralised testing using field test kits to check arsenic levels in soil and irrigation water, and collating data in a central database to facilitate real-time monitoring, can augment the remedial response to arsenic contamination.  The introduction of new technologies—such as Internet of Things (IoT) and machine learning—can transform early detection and mitigation of arsenic contamination. The application of IoT-based soil and water sensors along with machine-learning can aid in monitoring the arsenic levels continuously in rice-growing areas, and forecast high-risk zone areas to implement specific treatment measures. This will ensure irrigation cleanliness and reduce health risks from farm to fork.

One of the key challenges in addressing the arsenic crisis is lack of public awareness. The majority of consumers are unaware of the arsenic in rice and the long-term health risk its consumption poses. A common misconception is equating polished white rice with quality, overlooking the nutritive value of rice bought from branded outlets or local mandis      (marketplace) to be safe. However, even the rice varieties that are promoted as healthier options, for instance,      brown rice, tend to have higher levels of arsenic accumulated in the bran. This gap in awareness can be addressed through an education campaign in areas with high rice consumption. Arsenic level can be significantly reduced through simple cooking practicessuch as copious rinsing of rice and using extra water during boiling. For example, cooking interventions in Japan and Bangladesh, and cultivation in low arsenic soil have led to low arsenic exposure despite high rice consumption. 

The way forward needs to be strong, integrative, and policy-based. Beyond setting the safety standards of arsenic in rice, Food Safety and Standards Authority of India (FSSAI) could also consider creating a national roadmap for climate-resilient rice cultivation. This includes encouraging farmers to invest in climate-smart agriculture system that reduces arsenic uptake, along with inclusion in the national food security agenda. As India prepares to tackle the rising effects of climate change, the case of arsenic threat in rice indicates the pressing need for a holistic approach to address environmental, health, and agricultural challenges. There is an urgent need for proactive efforts to offer an antidote to the problem of arsenic contamination to reduce future health hazards and quality of staple grain, which matters for the food security of a nation.

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About the authors:

• Shoba Suri is a Senior Fellow with the Health Initiative at the Observer Research Foundation.
• Tanya Verma is an Intern at the Observer Research Foundation.

Source: This article was published by the Observer Research Foundation.

Observer Research Foundation

ORF was established on 5 September 1990 as a private, not for profit, ’think tank’ to influence public policy formulation. The Foundation brought together, for the first time, leading Indian economists and policymakers to present An Agenda for Economic Reforms in India. The idea was to help develop a consensus in favour of economic reforms.

 

New chlorophyll fluorescence imaging technique enables early detection of rice fungal diseases

Nanjing Agricultural University The Academy of Science

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The findings offer a non-invasive and efficient method for early disease detection, crucial for timely intervention and better disease management.

Rice is a vital global food staple, contributing significantly to daily calorie intake. However, up to 30% of annual rice yield is lost due to diseases, with rice blast and brown spot being among the most destructive fungal diseases. Accurate early detection of these diseases is challenging due to the similarity in their visual symptoms at the pre-symptomatic stage. Traditional molecular methods, while precise, are time-consuming and not easily scalable for field applications. In contrast, ChlF imaging, which measures the light emitted by chlorophyll molecules during photosynthesis, has emerged as a promising tool for detecting early plant stress before visible symptoms appear. This study aimed to harness ChlF imaging for distinguishing rice blast and brown spot at the early stages of infection.

A study (DOI: 10.1016/j.plaphe.2025.100012) published in Plant Phenomics on 15 February 2025 by Jae Hoon Lee’s team, Seoul National University, provides a powerful, non-destructive tool for diagnosing rice fungal diseases at the pre-symptomatic stage.

The study employed pulse-amplitude modulation (PAM) ChlF imaging to monitor changes in rice leaves infected with rice blast and brown spot. A total of 120 leaves and 750 spots were analyzed across five time points in detached leaf assays. The experimental setup involved treating rice leaves with conidial suspensions of Magnaporthe oryzae and Cochliobolus miyabeanus at various concentrations. The ideal concentrations of 5 × 10^4 for M. oryzae and 1 × 10^3 for C. miyabeanus were selected, as they induced individual lesions while maintaining comparable disease severity. Disease progression was categorized into asymptomatic, pre-symptomatic, and symptomatic stages based on lesion appearance, with visual inspection confirming the distinct patterns for each disease. ChlF images were taken at different time points, and 98 ChlF parameters were analyzed using principal component analysis (PCA), revealing a divergence in ChlF patterns between healthy and infected leaves, particularly during the pre-symptomatic stage. Significant increases in photochemical quenching parameters were noted in both diseases, with rice blast showing unique decreases in non-photochemical quenching (NPQ) and qN parameters, which were not observed in brown spot. Machine learning techniques were employed to classify ChlF data, achieving high classification accuracies (over 92%) at both leaf and lesion levels. The study identified several key ChlF parameters, including Rfd_L2, QY_Lss, and qP_Lss, as reliable diagnostic indicators for early disease detection. Validation through whole-plant assays confirmed the efficacy of these parameters, with rice blast-specific indicators showing distinct patterns compared to brown spot. These findings suggest that ChlF imaging is a powerful tool for early, non-invasive detection of rice fungal diseases, facilitating timely disease management and intervention.

This study underscores the potential of ChlF imaging as an early diagnostic tool for rice fungal diseases, offering a non-invasive, scalable, and accurate method for disease detection. By identifying distinct ChlF signatures for rice blast and brown spot, the research paves the way for more efficient disease management practices, enhancing rice production and contributing to global food security.

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References

DOI

10.1016/j.plaphe.2025.100012

Original Source URL

https://doi.org/10.1016/j.plaphe.2025.100012

Funding information

This work was supported by Rural Development Administration of Korea (RS-2022-RD010059) and Creative-Pioneering Researchers Program by Seoul National University.

About Plant Phenomics

Science Partner Journal Plant Phenomics is an online-only Open Access journal published in affiliation with the State Key Laboratory of Crop Genetics & Germplasm Enhancement, Nanjing Agricultural University (NAU) and distributed by the American Association for the Advancement of Science (AAAS). Like all partners participating in the Science Partner Journal program, Plant Phenomics is editorially independent from the Science family of journals. Editorial decisions and scientific activities pursued by the journal's Editorial Board are made independently, based on scientific merit and adhering to the highest standards for accurate and ethical promotion of science. These decisions and activities are in no way influenced by the financial support of NAU, NAU administration, or any other institutions and sponsors. The Editorial Board is solely responsible for all content published in the journal. To learn more about the Science Partner Journal program, visit the SPJ program homepage.

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Journal

Plant Phenomics

DOI

10.1016/j.plaphe.2025.100012 

Method of Research

Experimental study

Subject of Research

Not applicable

Article Title

Pre-symptomatic diagnosis of rice blast and brown spot diseases using chlorophyll fluorescence imaging

 

Hidden in plain sight: A century-old museum specimen turns out to be a landmark in evolution

Harvard University, Department of Organismic and Evolutionary Biology

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image: 

Artistic environmental reconstruction of the Montceau-les-Mines Lagerstätte (one of the two sites Palaeocampa is found) with Palaeocampa anthrax. A large Palaeocampa anthrax is depicted at the edge of a shallow inland streambed, shadowed by the lush vegetation and mist of a coal forest, flanked by several euthycarcinoids, Sottyxerxes multiplex, and a pair of freshwater xiphosurans, Alanops magnificus. 

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Credit: Original artwork by Christian McCall

In a twist worthy of a detective novel, a long-misidentified fossil at Harvard’s Museum of Comparative Zoology (MCZ) has emerged as a key discovery in early animal evolution. Originally described in 1865 as a caterpillar, Palaeocampa anthrax shuffled between classifications—worm, millipede, and eventually a marine polychaete—until 130 years later, when researchers realized its true identity: the first-known nonmarine lobopodian and the earliest one ever discovered.

Lobopodians are extinct, soft-bodied creatures that bridge the evolutionary gap between a primitive worm-like ancestor and modern arthropods like insects and crustaceans. Known mostly from Cambrian marine deposits such as Canada’s Burgess Shale, they include iconic fossils like Hallucigenia and Aysheaia pedunculata discovered in 1911, and were thought to be exclusively marine—until now.

A new study published in Communications Biology led by Richard Knecht, a former graduate student (PhD ’25) in Harvard's Department of Organismic and Evolutionary Biology (OEB), redescribes Palaeocampa anthrax as the first nonmarine and youngest lobopodian discovered; predating the famous Burgess Shale lobopodians by nearly fifty years.

“Lobopodians were likely a common sight on Paleozoic sea beds,” said Knecht, “but apart from microscopic tardigrades and terrestrial velvet worms, we thought they were confined to the ocean.”

Knecht, currently a postdoctoral fellow at the University of Michigan and an associate of the MCZ, discovered Palaeocampa while examining fossil millipedes in the MCZ collection. He noted legs on every trunk —ruling out caterpillar or worm—and recognized it as a lobopodian.

To confirm this, the team analyzed 43 specimens from two Carboniferous Lagerstätten—Mazon Creek (USA) and Montceau-les-Mines (France) —using advanced imaging, including backscatter scanning electron microscopy (SEM) and energy-dispersive spectroscopy. They revealed exquisite anatomical features—most notably, nearly 1,000 bristle-like spines covering the body.

Co-author Nanfang Yu, associate professor of physics at Columbia University, used Fourier-transform infrared spectroscopy (FTIR) to detect chemical residues at the spine tips—suggesting the spines secreted toxins to deter predators in its swampy habitat.

"What amazed me is that fragments of biomacromolecules could be exceptionally preserved or altered to geomacromolecules in fossils,” Yu said. “ I’m thrilled this technique possessed the sensitivity and specificity to differentiate fossilized remains from the rocky substrate.”

Palaeocampa’s closest relative is Hadranax, a Cambrian lobopodian from Greenland, nearly 200 million years older. Both had ten pairs of legs, no claws and were blind. But while Hadranax was unarmored and navigated the deep sea using elongated frontal appendages, Palaeocampa, at just four centimeters long, bore a dense coat of spines—arranged above each pair of legs, giving it a fuzzy caterpillar-like appearance—and inhabited freshwater, possibly amphibious, environments.

Palaeocampa’s discovery also resolves the mystery of France’s Montceau-les-Mines fossil site, once considered as marine. “Mazon Creek is a mix of terrestrial, freshwater, and marine animals,” Knecht explained. “But, Montceau-les-Mines, where half of the specimens come from, was hundreds of kilometers inland, with no ocean present.” Its reclassification confirms the site’s nonmarine setting, offering a rare glimpse into ancient freshwater ecosystems.

This discovery broadens our understanding of lobopodian diversity and raises new evolutionary questions: How many others made the leap from marine to freshwater and could more be hiding, misidentified, in museum drawers?

“The conditions required to fossilize soft-bodied creatures like lobopodians are rare,” Knecht noted. “Most of our insights come from Cambrian Lagerstätten, but the Carboniferous period—when Palaeocampa lived—offers far fewer such windows, making every new find incredibly valuable.”

This breakthrough came from reexamining century-old specimens from museums including the MCZ, Yale Peabody Museum, the Smithsonian National Museum of Natural History, France’s Muséum d’histoire naturelle d’Autun, the Chicago Field Museum, and the University of Illinois Urbana-Champaign—highlighting the ongoing scientific value of museum collections.

Ironically, Palaeocampa sat for decades in a drawer just feet from the office of Stephen Jay Gould’s office—MCZ curator and author who popularized the Cambrian oddities in Wonderful Life. “It was literally hiding in plain sight,” Knecht said. “Sometimes, the biggest discoveries are the ones waiting to be looked at again.”

Neotype of Palaeocampa anthrax from the Mazon Creek Lagerstätte and rediscovered in the Invertebrate Paleontology collection of the MCZ.  The faint red and blue grid lines from a wax pencil can still be seen across the specimen, made by the nineteenth century artist Katherine Pierson who illustrated this specimen for Samuel Scudder in 1884.

Credit

Richard J. Knecht

Journal

Communications Biology

DOI

10.1038/s42003-025-08483-0 

Article Title

Palaeocampa anthrax, an armored freshwater lobopodian with chemical defenses from the Carboniferous. Communications Biology

A fossil’s 150-year journey from misidentification to evolutionary insight

University of Michigan

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A fossil specimen misidentified since its discovery during the Civil War and correctly identified by a University of Michigan researcher reveals an evolutionary leap: It marks the first time this line of sea creatures is known to have left the ocean.

 

U-M postdoctoral fellow Richard J. Knecht found that the specimen, identified as a seaworm for well over a century, is actually a kind of invertebrate called a lobopod. Lobopods are soft-bodied invertebrates that closely resemble a "worm with legs," according to Knecht, who led the work as a researcher at Harvard University.

 

Lobopods are considered the ancestor to all arthropods—all insects, spiders and crustaceans—and scientists have long thought that  lobopods, which first appeared in the fossil record more than 500 million years ago, only lived in marine environments. 

 

Now, Knecht suggests that the specimen, named Palaeocampa anthrax, likely lived in a freshwater environment. Knecht also found the specimen likely had chemical defenses that suggest it may have spent at least part of its time on land. The study, which was supported by the National Science Foundation, was published in Communications Biology.

 

"This is the first evidence that we have that this group actually did leave the ocean. Transitioning from a saltwater environment, even to a freshwater environment, is a major evolutionary step," Knecht said. "Any time you find a group that made this transition, it's not just insightful, it's really important evolutionarily to try to understand how this happened."

 

Knecht says his study also shows the importance of revisiting fossil collections, even fossils that have been previously identified, with fresh perspectives and updated techniques. Since its discovery, this specimen has been variously misidentified as a caterpillar, a marine worm, and a millipede—organisms from very different evolutionary lineages. Even recent studies cited photographs of the fossil without recognizing its true identity.

 

"When the specimen was first discovered, lobopods didn't even exist as a group. This is an example of why revisiting older specimens can be of real value," said Knecht, a researcher in the U-M Department of Ecology and Evolutionary Biology and Museum of Paleontology. "Even specimens that are iconic and super well known—provide an opportunity to make big discoveries just by viewing them with new techniques and fresh perspectives."

 

Palaeocampa anthrax and new techniques

 

Knecht first encountered the specimen while looking at a collection of millipedes in the Invertebrate Paleontology Department of the Museum of Comparative Zoology at Harvard University. He immediately recognized it as a species of lobopod—not a millipede as it was labeled in the drawer.

 

Paleozoic lobopods can be difficult to pin down, Knecht said. This species looks superficially like woolly bear caterpillars, with papillae and bristles of spikes growing off the trunks of their bodies. Some lobopods from this era had plates of armor, some had forward-facing arms prodruding from their heads. One species' body is absent of features and just looks like a straw with smooth straw-like legs.

 

But when Knecht looked at the Palaeocampa specimen, he noticed several noticeable differences from other lobopodian species. For example, most lobopodian spines exhibit a cone-in-cone growth pattern like a stack of traffic cones coming to a point at the tip. Instead, Palaeocampa's spines look like a series of rigatoni growing out of its trunk, each segmented like bamboo, with a top that looks like a castle turret, Knecht said.

 

Then, the research team noticed orange halos at the tips of the preserved spines. The team wondered if there was a fluid or chemical that the lobopod may have emitted from the tips of its spines.

 

To investigate this, Knecht worked with Nanfang Yu, a physicist at Columbia University. Yu used a technique called FTIR spectroscopy and infrared light to determine that there were fossilized molecules present at the tips of the specimen's spines that weren't present anywhere else along the spine or in the rock. This suggests, Knecht says, that there was a chemical specifically emanating from the tip of the spine.

 

This characteristic is the most significant evidence indicating that the lobopod was likely amphibious, Knecht said. Most marine or aquatic organisms that have spines with chemical defense systems have spikes that they can use to inject predators. If their defense systems emanated from an open tip, their chemical defense would be less effective and simply dilute in the water.

 

"If I were to place a chip on the table, I'd say this organism was probably more terrestrial or amphibious, specifically because of that tip. It makes more sense in an aerial rather than a subaqueous environment," he said.

 

Statistical miracles

 

Lobopodians are rare in the fossil record especially after the Cambrian Period, Knecht said. Because invertebrates have no bones, their soft bodies degrade very quickly after death. An unusual set of circumstances has to exist in order for them to fossilize: They have to die and then quickly be buried before scavengers or decomposition takes hold, often in aquatic environments with fine grains or mud and little oxygen.

 

All known lobopodians come from Lagerstätten—extraordinary fossil sites with the rare geological conditions needed to preserve soft-bodied organisms in exceptional detail and abundance. Palaeocampa anthrax was discovered both at Mazon Creek, Illinois, and Montceau-les-Mines, France, both Lagerstätten renowned for their fossils. 

 

This specimen is one of two lobopodians from the Carboniferous, the last period within the Paleozoic—and represents the youngest fossil lobopodian species yet discovered. It's also a transition fossil, an example of a species that represents an evolutionary leap. 

 

Trying to find transition fossils is extraordinarily difficult, Knecht said. They often occur during a small snapshot of time, geologically speaking. It's even more difficult to discover transition fossils of invertebrates; their lack of bones means they don't preserve well in the fossil record. Finding one is a stroke of luck. To capture the Palaeocampa fossil in such detail, recording chemicals emanating from its tips, its preservation must have been almost instantaneous, Knecht said. It likely was buried alive in the mud.

 

"It's like winning the lottery not once, but three times. First, that the site existed at all; second, to have this level of preservation; and third, to then find it over 300 million years later," he said. "It's a series of statistical miracles."

 

Study: Palaeocampa anthrax, an armored freshwater lobopodian with chemical defenses from the Carboniferous. DOI: doi.org/10.1038/s42003-025-08483-0

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Journal

Communications Biology

DOI

10.1038/s42003-025-08483-0