Andrew A. Meharg’s research while affiliated with Queen's University Belfast and other places

Neurodevelopmental disorders are increasing globally, and metal exposure may play a significant role as an environmental factor. This cross-sectional study aimed to identify metal mixture patterns and assess their impact on children’s neurodevelopment. Data from 962 children (aged 4–5 years) participating in the Spanish INMA cohort study were analysed. Urinary metal concentrations (cobalt (Co), copper (Cu), molybdenum (Mo), selenium (Se), lead (Pb), zinc (Zn), and arsenic speciation) were used as exposure biomarkers. Principal component analysis (PCA) revealed four latent exposure variables representing uncorrelated metal mixture patterns. Linear regression analyses examined the associations between these variables and children’s neuropsychological functions assessed through the McCarthy Scales of Children’s Abilities. The first latent exposure variable (Cu, Se, Pb, Zn) and the second (inorganic arsenic, monomethylarsonic acid) showed negative associations with verbal executive function (ß = − 1.88, 95% confidence interval (CI) = − 3.17 to − 0.59) and gross motor function (ß = − 1.41, 95% CI = − 2.36 to − 0.46), respectively. Conversely, the third variable (Mo, Co) and the fourth (arsenobetaine) exhibited positive associations with visual and verbal span functions (ß = 1.14, 95% CI = 0.16 to 2.12) and fine motor function (ß = 1.01, 95% CI = 0.11 to 1.92), respectively. This study suggests that even relatively low levels of metal latent exposures, notably inorganic arsenic and a mixture of metals including Pb, adversely affect children’s neuropsychological development function scores, while exposure to arsenobetaine and a mixture of Co and Mo has a positive impact.

Previous studies have shown that arsenic and cadmium can accumulate in rice grain to levels that cause health concerns. Furthermore, geographical survey has shown that there is considerable variation (~ 100-fold) in accumulation of these carcinogens in rice grain. This variance must be due to heterogeneity in soil biogeochemistry and contrasting rice management regimens. Here we present the first systematic global study to investigate the impact of soil biogeochemistry on accumulation of these elements in rice grain. Matched grain, shoot, root and soil samples were collected across a latitudinal gradient from East Africa to Europe and soil, shoot, grain chemistry and soil microbial community (prokaryotes and fungi) assessed within the context of arsenic and cadmium biogeochemistry. European and Vietnamese grain sum of arsenic species (inorganic arsenic plus dimethylarsonic acid) concentration medians, ~ 0.1 mg/kg, were found to be around ten-fold higher compared to those in East Africa and Sri Lanka. Arsenic concentrations were linked to higher levels of soil arsenic, and to higher abundance of soil sulphur-oxidising and sulphate reducing bacteria and methanogenic archaea. For cadmium, Sri Lanka showed highest (median 0.0156 mg/kg) and Europe lowest (median of 0.001 mg/kg) levels in grain, with the other regions showing intermediate values. Interestingly, grain cadmium was unrelated to soil cadmium concentrations, with Europe having the highest levels of cadmium in soil. Instead, grain cadmium correlated with higher oxidation/reduction potential, lower -log[hydrogen ion], lower soil calcium, and to a higher abundance of aerobic bacteria and fungi (lowest abundance of these organisms in European soils).

Here is presented a study to investigate the geographic variation in rice grain nutrients (trace and macro-elements and vitamins) and toxicants (arsenic species and cadmium) across a contiguous strip of 36 districts that constitute western Bangladesh. The survey collected ~ 500 market rice samples, averaging 15 samples and 10.7 cultivars per district. New LC-MS methods were developed for rice relevant, B and E complex compounds. Cadmium and zinc decreased southward, while copper, DMA, inorganic arsenic and oryzanols decreased northwards. There was a longitudinal gradient for iron, potassium, and vitamin B6. The greatest changes ~ twofold for cadmium and vitamin B6, and 1.5 for zinc across these gradients. The gradients may be driven by climate, geographical setting, soils, or cultivar, or a combination of all. The most obvious gradient was the transition from high to low altitude and from Pleistocene to Holocene soils as land transitioned from the upland plains of the north to sea-level in the south. Rice is a very important source of copper, phosphorus, vitamin B1, and zinc, and to a lesser extent iron, B3, B6, potassium. It is a poor source of vitamin E and calcium.

Even relatively low levels of metals exposure may impact health, particularly among vulnerable populations such as infants and young children. However, little is known about the interplay between simultaneous metal exposures, common in real-life scenarios, and their association with specific dietary patterns. In this study, we have evaluated the association between adherence to Mediterranean diet (MD) and urinary metal concentrations individually and as an exposure mixture in 713 children aged 4-5-years from the INMA cohort study. We used a validated food frequency questionnaire to calculate two MD indexes scores: aMED and rMED. These indexes gather information on various food groups within the MD and score differently. To measure urinary concentrations of cobalt, copper, zinc, molybdenum, selenium, lead, and cadmium as exposure biomarkers, we used inductively coupled plasma mass spectrometry (ICP-MS), coupled with an ion chromatography (IC) equipment for arsenic speciation analysis. We applied linear regression and quantile g-computation, adjusted for confounders, to analyse the association between MD adherence and exposure to the metal mixture. High adherence to MD such as the quintile (Q) 5 MD was associated with higher urinary arsenobetaine (AsB) levels than Q1, with β values of 0.55 (confidence interval - CI 95% 0.01; 1.09) for aMED and 0.73 (CI 95% 0.13; 1.33) for rMED. Consumption of fish was associated with increased urinary AsB but reduced inorganic arsenic concentrations. In contrast, the aMED vegetables consumption increased urinary inorganic arsenic content. A moderate level of adherence to MD (Q2 and Q3) was associated with lower copper urinary concentrations than Q1, with β values of -0.42 (CI 95% -0.72; -0.11) for Q2 and -0.33 (CI 95% -0.63; -0.02) for Q3, but only with aMED. Our study, conducted in Spain, revealed that adhering to the MD reduces exposure to certain metals while increasing exposure to others. Specifically, we observed increase in exposure to non-toxic AsB, highlighting the significance of consuming fish/seafood. However, it is crucial to emphasize the necessity for additional efforts in reducing early-life exposure to toxic metals, even when adhering to certain food components of the MD.

To investigate how soil fertilization/amendments alters arsenic speciation grain off-take in paddy rice, rice was grown to maturity in growth chambers fertilized with standard mineral fertilizer, wood ash (rich in silica), pig slurry (rich in organic matter), and non-amended control. The soil was sourced from a Chinese paddy field. The primary fertilized elements (nitrogen, phosphorus, potassium) were kept constant across treatments. Porewater chemistry and soil microbiology were monitored throughout the experiments. Total grain arsenic, sum of inorganic arsenic and dimethylarsinic acid (DMA), was significantly different between treatments (P = 0.024), with inorganic arsenic varying from 0.025 to 0.08 mg/kg and DMA from 0.08 to 0.16 mg/kg for control compared to fertilized, respectively. Fertilizer source made no difference to arsenic speciation concentration in grain. Porewater analysis found that as anaerobism set in, inorganic arsenic, phosphorus and manganese greatly lowered in concentration. Methylated arsenic species concentrations increased over time, concurrent with an increase in pH, decrease in Eh, and increase in total organic carbon and iron, with no strong treatment effects, except for pig slurry that enhanced pH and decreased Eh. Methanogenic archaea, sulfate-reducing bacteria and Acidobacteria increased with time and some Actinobacteria and Firmicutes increased due to slurry, but then decreased with time (P < 0.01). Methanogenic archaea and sulphate-reducing bacteria correlated positively with porewater DMA and negatively with porewater inorganic arsenic (P < 0.05). Genera within the Actinobacteria and Burkholderiaceae correlated negatively with DMA, while genera with iron-reducing capacity (Clostridiales) correlated positively with porewater inorganic arsenic and DMA (P < 0.05).

In Bangladesh most agronomic biomass (straw, husk, dried dung) is burnt for domestic cooking use. Consequently, the soil is continuously stripped of mineral nutrients and carbon (C) substrate. Here we investigate if recycling of household ash (ash) as fertilizer can sustainably improve soil fertility as well as minimise accumulation of toxic elements (As, Cd) in rice grain. Large scale field trials across two geographic regions (Barind, Madhupur) and two seasons (wet, dry) and with application of 3 fertiliser treatments (NPKS, ash, NPKS + ash) were conducted. At the end of each season, the impact of region*season*treatment on soil microbial comunities, rice yield, and grain quality (As, Cd, nutrient elements) was assessed. When compared to conventional field application rates of NPKS (control), application of ash boosted rice yield by circa. 20% in both regions during wet and dry season, with no effect on rice grain carcinogenic inorganic arsenic (iAs), dimethylarsonic acid (DMA) or cadmium (Cd), but with potential to increase zinc (Zn). For soil microbial communities, a significant region and season effect as well as correlation with elements in rice grain was observed, amongst these Cd, Zn, iAs and DMA. This study illustrates that application of ash can reduce the requirement for expensive chemical fertiliser, whilst at the same time increasing rice yield and maintaining grain quality, making farming in Bangladesh more sustainable and productive. The study also implies that the combined impact of region, season, and soil microbes determines accumulation of elements in rice grain. Supplementary Information The online version contains supplementary material available at 10.1007/s12403-023-00539-y.

Environmental selenium deficiency and toxicity can result in Keshan disease and selenosis, respectively. Due to dietary preferences, milk is considered a primary source of selenium, where, in controlled environments milk selenium concentration reflects the selenium provided in fodder to lactating cows. However, the movement of selenium through agroecosystems is not well understood. Therefore, the aim of this current study was to investigate variables that are responsible for transfer of selenium from soil to milk. Investigated parameters include spatial variability, soil selenium status, season, herd diet and husbandry of cattle. Farm-based sample collections were carried out, where soil, grass, silage and milk were collected over forty-eight geographically spaced locations over Northern Ireland during both summer and winter. Selenium concentrations were determined using ICP-MS. Median selenium concentrations for soil (0.46 mg/kg DM), grass (0.06 mg/kg DM) silage (0.03 mg/kg DM) and milk (0.23 mg/kg DM). Results showed that soil selenium concentrations were significantly affected by the pH and organic matter composition of soil. Additionally, a statistically significant relationships between soil and grass selenium concentrations were also found. Despite these strong environmental relationships with grass, these relationships were not reflected in the milk selenium concentrations, indicating a disconnect between the selenium concentration in the agricultural environment and the milk from which it is derived. Selenium was higher in milk in winter months as compared to summer, related to supplemental feed practices over the winter when cows are housed. This study highlighted that cattle feed supplementation of feed with selenium, an essential element, was an effective way of enhancing dietary exposure through a commonly consumed foodstuffs derived from dairy.