Clinical Pharmacist and Master’s student in Clinical Pharmacy with research interests in pharmacovigilance, behavioral interventions in mental health, and AI applications in clinical decision support. Experience includes digital health research with Bloomsbury Health (London) and pharmacovigilance practice in patient support programs. Published work covers drug awareness among healthcare providers, postpartum depression management, and patient safety reporting. 
Clinical Pharmacist and Master’s student in Clinical Pharmacy with research interests in pharmacovigilance, behavioral interventions in mental health, and AI applications in clinical decision support. Experience includes digital health research with Bloomsbury Health (London) and pharmacovigilance practice in patient support programs. Published work covers drug awareness among healthcare providers, postpartum depression management, and patient safety reporting. What was studied?
This study measured mercury in vegetables and grains grown on farms within 10 km of two coal-fired power plants, alongside paired soil sampling, to quantify contamination levels against food safety thresholds and to identify likely exposure pathways. Investigators analyzed total mercury in common leafy vegetables (lettuce, amaranth, water spinach), fruiting vegetables (tomato, eggplant, pepper, cucumber, cowpea), and grains (rice, maize), then compared results with “control” foods sourced >55 km away. They also examined how mercury varied with distance from plants, whether plant mercury tracked soil mercury, and how mercury partitioned across plant organs (using tomato as a model). Finally, they tested whether simple rinsing reduces mercury in leafy vegetables and estimated probable weekly intake (PWI) for residents consuming mostly self-grown produce, contextualized against the WHO Provisional Tolerable Weekly Intake (PTWI).
Who was studied?
The research did not study human participants directly; it studied food and environmental samples representing real dietary inputs for local populations. Samples came from six open-field locations (A1–A2 near Plant A; B1–B4 near Plant B) and included pooled plant and soil composites (about 20 individual plants per pooled crop sample, and similarly pooled soil samples) collected in 2015, plus grocery-store control samples from a distant area (>55 km). The “population” for exposure assessment was modeled as local residents—especially farming households—who obtain >95% of vegetables and grains from their own farmland, using standard consumption rates and average adult body weight applied in the authors’ PWI calculations.
Most important findings
Across these farming areas, mercury in vegetables and grains frequently exceeded Chinese maximum limits, and the spatial pattern strongly implicated coal-plant proximity and atmospheric deposition onto leaves as major drivers, with washing offering partial reduction for leafy crops.
| Critical point | Details |
|---|---|
| Exceedance rates relative to food standards | 79% of vegetable samples exceeded the 10 μg/kg FW limit and 67% of grain samples exceeded the 20 μg/kg FW limit; the highest measured levels were 8.6× (vegetables) and 6.3× (grains) above allowed limits, while distant grocery controls did not exceed limits. |
| Soil gradient with distance from power plants | Soil mercury averaged ~305 μg/kg at 1 km (Plant A) and ~383 μg/kg at 1 km (Plant B), declining with distance (negative correlation; R²≈0.82) and exceeding control/background by >10×, indicating a strong local source signal relevant to site-based certification risk. |
| Crop-specific accumulation patterns | Leafy vegetables showed especially high concentrations (e.g., water spinach highest among tested leafy crops), and grains differed (rice > maize), implying that certification programs should treat commodity type as a primary risk stratifier rather than assuming uniform uptake across crops. |
| Evidence for air-to-leaf deposition as a key pathway | In tomatoes, mercury was far higher in leaves (~116 μg/kg) than fruits (~29 μg/kg) or roots (~14 μg/kg), supporting the interpretation that atmospheric deposition (fly ash/particulate Hg) onto foliage can dominate, especially near relatively new plants (<5 years operation). < td> |
| Washing meaningfully reduces, but does not eliminate, risk | Simple water rinsing reduced mercury in lettuce and amaranth leaves by ~19–63%, consistent with removable surface deposition; however, post-wash values often still exceeded the 10 μg/kg limit, meaning “wash to comply” is unreliable for certification. |
| Intake estimates exceed toxicological guidance | Using 95th-percentile concentrations, modeled PWI was ~2.67 μg/kg bw/week from vegetables and ~1.69 from grains, totaling ~4.36 μg/kg bw/week, above the WHO PTWI (1 μg/kg bw/week), flagging chronic exposure concerns relevant to consumer-protection thresholds. |
Key implications
For HMTC-style programs, mercury in vegetables should trigger location-aware compliance rules because proximity to coal combustion sources can drive frequent exceedances and higher modeled intake. Primary regulatory impacts include prioritizing fenceline-to-10 km agricultural sourcing audits and enforcing commodity-specific action levels, especially for leafy greens and rice. Certification requirements should emphasize validated sampling plans (soil plus edible tissue) and require evidence-based preprocessing claims since rinsing reduces but often does not normalize mercury. Industry applications include supplier zoning, crop selection guidance, and mitigation via emission/fly-ash controls. Research gaps include separating air vs root contributions and speciation (methyl vs inorganic) for crops. Practical recommendations include routine surveillance near emitters, clear consumer labeling for high-risk regions, and conservative pass/fail thresholds aligned to intake-based risk.
Citation
Li R, Wu H, Ding J, Fu W, Gan L, Li Y. Mercury pollution in vegetables, grains and soils from areas surrounding coal-fired power plants.Scientific Reports. 2017;7:46545. doi:10.1038/srep46545
Mercury (Hg) is a neurotoxic heavy metal found in various consumer products and environmental sources, making it a major public health concern. Its regulation is critical to protect vulnerable populations from long-term health effects, such as neurological impairment and cardiovascular disease. The HMTC program ensures that products meet the highest standards for mercury safety.
