The research team, led by Nitika Rani with Pooja Arora and Smita Chaudhry as senior authors, set out to answer a question that affects millions of people across the developing world. As freshwater supplies grow scarcer, farmers increasingly turn to wastewater as a reliable, nutrient-rich alternative for irrigation. But that convenience carries a hidden cost: industrial and municipal effluents can carry chromium, lead, cadmium, copper, and nickel into the food chain, where they concentrate in the edible tissues of plants that people eat, often with minimal processing.

What makes the new study distinctive is its controlled comparative design. Rather than sampling vegetables from fields where countless variables confound the results, the researchers grew their test crops in pots under controlled conditions, irrigating them with water drawn from five distinct sources: effluent after primary treatment, after secondary treatment, and after tertiary treatment, plus raw drain water and clean groundwater. This allowed them to isolate the effect of water quality on metal uptake with unusual precision, and it represents one of the first head-to-head comparisons of primary, secondary, and tertiary-treated wastewater for vegetable cultivation under such conditions.

The water analysis produced a picture that was, on the surface, reassuring. Concentrations of chromium, lead, cadmium, and copper in every irrigation source remained within the permissible limits set by international guidelines. Only nickel broke the rules, exceeding the recommended threshold in drain water. Soil samples told a similar story: heavy metal concentrations in the growing medium stayed within safety thresholds across all treatments. If the analysis had stopped there, the conclusion would have been that treated wastewater is safe for growing food.

But the vegetables told a different story. When the researchers measured metal levels in the harvested fenugreek, spinach, and mustard, they found that chromium, ranging from 5 to 20 milligrams per kilogram, lead at 2.5 to 12.5 milligrams per kilogram, and cadmium at 0.5 to 1.5 milligrams per kilogram occasionally surpassed the limits established by the Codex Alimentarius Commission of the FAO and WHO and by WHO guidelines from 2007. In other words, water and soil that passed regulatory muster still produced vegetables that sometimes failed it.

The explanation lies in plant physiology. Leafy vegetables are among the most efficient accumulators of heavy metals because of how they take up and transport nutrients. Plants possess metal transport systems designed to shuttle essential elements like copper and zinc from roots to shoots, and these same pathways cannot fully distinguish essential micronutrients from toxic neighbors on the periodic table. Spinach, in particular, proved to be an aggressive accumulator. The bioconcentration factor, a ratio comparing metal concentration in plant tissue to that in soil, exceeded the critical value of 1 for both lead and copper in spinach, meaning the plant actively concentrated these metals in its leaves above the levels found in the ground it grew in.

The health risk calculations sharpened the concern. The researchers estimated the daily intake of metals for both adults and children consuming these vegetables and found that children consistently faced higher exposure per unit of body weight. The highest intakes were recorded for nickel in spinach, at 0.04 milligrams per kilogram of body weight in children and 0.03 in adults, followed closely by copper, at 0.015 milligrams per kilogram in children and 0.013 in adults. Because children eat more food relative to their body mass and their developing nervous systems are particularly vulnerable to neurotoxic metals like lead and cadmium, this disparity matters for public health planning.

The hazard index, which aggregates the non-carcinogenic risk from multiple exposure pathways, crossed into the danger zone for specific vegetable-metal combinations. Nickel in spinach and lead in both mustard and fenugreek produced hazard index values indicating a heightened risk of non-carcinogenic health effects, which can include damage to the kidneys, nervous system, and cardiovascular system over years of chronic exposure. While the study did not assess carcinogenic risk, chronic lead and cadmium exposure are both associated with serious long-term outcomes, and no safe blood lead level has been identified by health authorities.

Perhaps the most consequential finding is the disconnect between water quality compliance and food safety. The treated effluents used in the experiment met the relevant standards for irrigation water, yet the crops they nourished still occasionally exceeded food safety limits. This suggests that current wastewater treatment and reuse guidelines, which focus on the water itself, may not adequately protect consumers of leafy vegetables. Metals that fall below detection thresholds of concern in water can still accumulate over a growing season, and the bioconcentration behavior of species like spinach amplifies the exposure. The implication is that safety standards may need to account for the crop type, not just the water source, with leafy accumulators like spinach warranting stricter scrutiny than fruiting or grain crops.

For the millions of urban and peri-urban farmers who depend on wastewater irrigation, the study does not call for an outright ban but for smarter management. The results point toward crop selection as a practical intervention: choosing vegetables that accumulate fewer metals, or reserving treated wastewater for non-food crops, could reduce risk without eliminating a water resource that many communities cannot afford to lose. The researchers emphasize that their controlled pot design, while powerful for isolating variables, now needs to be complemented by field-scale studies that capture the full complexity of real farming systems. As water scarcity intensifies across South Asia and beyond, the question of what flows onto the fields, and what ends up on the plate, is becoming one of the most important food safety issues of the coming decade.

Subject of Research: Heavy metal accumulation in leafy vegetables irrigated with treated and untreated wastewater and associated food safety and health risks

Article Title: Heavy metal contamination in wastewater-irrigated leafy vegetables: implications for food safety

Article References: Rani, N., Arora, P., & Chaudhry, S. (2026). Heavy metal contamination in wastewater-irrigated leafy vegetables: implications for food safety. Environmental Monitoring and Assessment, 198(10), Article 1135. https://doi.org/10.1007/s10661-026-15939-1

Image Credits: AI Generated

DOI: 10.1007/s10661-026-15939-1

Keywords: heavy metals, wastewater irrigation, leafy vegetables, spinach, food safety, bioconcentration factor, health risk assessment, daily metal intake, hazard index, nickel, lead, cadmium

The research team, led by Sarah J. McLaren of Massey University alongside Graham A. McAuliffe, Thomas C. Ponsioen, Ratna C. Purwestri, Flaminia Ortenzi, and Ty Beal, addressed a persistent blind spot in nutritional life cycle assessment, or nLCA. Previous reviews had documented that most nLCA studies are concentrated in high-income countries, rely on nutrient indices developed from United States data, and suffer from a lack of consensus on how to define a nutritional functional unit. Indonesia, now the world’s sixteenth largest economy yet still home to a poverty rate of 9.4 percent unevenly spread across its islands, had virtually no local life cycle inventory data for its foods. Existing global meta-analyses leaned heavily on proxy data from other countries that poorly reflect Indonesian agroecological conditions, cooking practices, and waste treatment.

To close this gap, the researchers assessed 90 foods spanning five groups: animal-source foods; pulses, nuts, and seeds; starchy staples; vegetables; and fruits. The environmental side of the analysis covered seven impact categories from cradle to grave, meaning from primary production through post-harvest handling, processing, packaging, distribution, retail, home or street preparation, and finally waste treatment. The categories included climate change, scarcity-weighted water use, marine and freshwater eutrophication, terrestrial acidification, particulate matter formation, and land use. Crucially, the team modelled distinctly Indonesian realities: cooking on liquefied petroleum gas stoves, congee prepared as street food, and end-of-life treatment dominated by open dumping and burning.

The nutritional side employed the Nutritional Value Score, or NVS, a recently developed profiling system scaled from 1 to 100 that captures both essential nutrient density and protective factors against noncommunicable diseases. The NVS is the weighted mean of seven normalised dietary attributes: vitamins at 20 percent, minerals at 20 percent, protein at 12.5 percent, omega-3 fatty acids at 10 percent, fibre at 7.5 percent, calories at 7.5 percent, and nutrient ratios covering sodium to potassium, saturated to unsaturated fat, and carbohydrate to fibre at 22.5 percent, with a 25 percent penalty applied to ultraprocessed foods. Traditional Indonesian fermented foods such as tempeh and tofu are not classified as ultraprocessed and therefore escape the penalty. The functional unit was defined as 100 NVS, the highest nutritional value on the scale, of food as consumed, which required accounting for inedible fractions, cooking yield, and consumer waste when calculating the quantity of food that must be purchased.

The results expose enormous heterogeneity. Among animal-source foods, dairy products other than cheese achieved the highest enviro-nutritional efficiencies, while beef, lamb, rabbit, pork, and tilapia ranked lowest. Water use within this group ranged from 0.12 to 79.8 cubic metres per functional unit, and land use from 0.01 to 28.2 square-metre-years of crop equivalents. The drivers are well understood: enteric fermentation from ruminants generates methane, manure management produces nitrous oxide and contributes to eutrophication and acidification, and high feed conversion ratios inflate the footprint of monogastric meats. Economic allocation, which assigns most livestock system impacts to meat rather than to lower-value co-products, explains why chicken organs rank comparably to dairy products despite coming from the same birds.

In the pulses, nuts, and seeds group, cashews stood out for all the wrong reasons, showing the lowest efficiencies across most environmental categories, driven largely by poor fertiliser use efficiency in cashew cultivation. Soybean products, by contrast, achieved the highest efficiencies, aided by leguminous nitrogen fixation that reduces fertiliser requirements. Excluding cashews, variability in this group was modest for several categories but reached 211 times the lowest result for marine eutrophication, water use, and land use, while nutritional scores varied little, from 46 to 65, meaning the efficiency differences were almost entirely attributable to supply-chain activities rather than nutritional composition.

Among starchy staples, congee, the study’s only multi-ingredient food, performed three to five times worse than the next least efficient item across every category, a consequence of its high salt content as street food, an unfavourable carbohydrate-to-fibre ratio, and low overall nutrient density. White rice and rice noodles also ranked poorly, while whole wheat pasta and sweet corn performed best. Vegetables told a striking story: the five dark green leafy vegetables studied, including pumpkin leaves, drumstick leaves, sweet potato leaves, tree fern, and water spinach, achieved the highest efficiencies in the group, partly because they are low-value co-products assigned zero primary production burdens. Among fruits, imports from China ranked among the least efficient, primarily due to high water use, and durian emerged as a cautionary example: its skin comprises 76 percent of the fruit and carries more than half of its climate change impact through transport and methane emissions at end of life.

Across the life cycle, primary production dominated, contributing at least 30 percent of impacts for all categories and typically more than 95 percent for land use. Yet the relationship between nutritional value and environmental performance proved far from universal. Overall, the correlation between NVS and the enviro-nutritional single score was weak, with an R-squared of just 0.03. It was strongest for starchy staples, where per-kilogram impacts are relatively homogeneous so nutritional score drives the ranking, at R-squared 0.65, moderate for fruits at 0.30, weak for vegetables at 0.15, and effectively absent for animal-source foods at R-squared 0.00, where both nutritional value and environmental impact vary substantially and independently. The practical implication is that nutritional quality alone cannot predict environmental performance, and vice versa, particularly for animal products.

For Indonesian policy, the findings point toward concrete opportunities. The authors identify dark green leafy vegetables, chayote, carrots, papaya, guava, cantaloupe, milk, yogurt, chicken organs, whole grains, and soy products as nutritious foods with comparatively low environmental footprints. Four items, beef and chicken organs, edamame, mussels, and tuna, scored at least 65 on the NVS while ranking in the top 20 percent least impactful foods for four or more impact categories, marking them as candidates for local prioritisation. Beyond food choice, the study highlights improvements in preparation and waste management, such as reducing salt in congee and removing durian skins before distribution, alternative sourcing of domestically produced fruits and nuts, and supply-chain gains in fertiliser and irrigation efficiency. The authors caution, however, that these attributional results should be complemented by consequential analysis before recommending large dietary shifts, and that the approach requires contextualisation rather than oversimplified recommendations.

The study also delivers a substantial data contribution: an open-access life cycle inventory for Indonesian foods, built from Agri-footprint 6.3, ecoinvent 3.9.1, Agribalyse 3.1, and the World Food LCA Database 3.5, adapted with country-specific water flows and electricity grid mixes and prioritising geographical and technological representativeness. Limitations remain, including reliance on the largest supplier country for each food, inability to capture sub-national heterogeneity from Java’s volcanic soils to mountainous farming systems, and uncertainty in water scarcity characterisation factors and toxicity categories, which contributed more than half of the single score for 14 of the 90 foods. Future work should extend the method to composite dishes such as nasi goreng and soto, localise nutrient profiling weightings, and invest in sub-nationally disaggregated data on livestock, transport, and food losses. As a proof of concept, the study demonstrates that nLCA can counteract what the authors call carbon tunnel vision, replacing single-issue metrics with a nutritional lens that spans the entire food supply chain and can be adapted to other low- and middle-income countries striving to feed growing populations within planetary boundaries.

Subject of Research: Integrated enviro-nutritional life cycle assessment of commonly consumed local foods in Indonesia

Article Title: Integrated environmental and nutritional efficiencies of local foods in Indonesia: a cradle-to-grave enviro-nutritional life cycle assessment

Article References: McLaren, S. J., McAuliffe, G. A., Ponsioen, T. C., Purwestri, R. C., Ortenzi, F., & Beal, T. (2026). Integrated environmental and nutritional efficiencies of local foods in Indonesia: a cradle-to-grave enviro-nutritional life cycle assessment. The Lancet Regional Health – Western Pacific, 74, Article 101977. https://doi.org/10.1016/j.lanwpc.2026.101977

Image Credits: AI Generated

DOI: 10.1016/j.lanwpc.2026.101977

Keywords: life cycle assessment, Indonesia, nutrition, food systems, Nutritional Value Score, sustainable diets, environmental impacts, greenhouse gas emissions, animal-source foods, leafy vegetables, food policy, Southeast Asia