Heavy Metals in Soil and Salad in the Proximity of Historical Ferroalloy Emission

Agricultural Mitigation Strategies to Reduce the Impact of Romaine Lettuce Contamination

BACKGROUND

Leafy greens, particularly romaine lettuce, are often associated with outbreaks due to their susceptibility to contamination from various environmental sources. This study aimed to evaluate the presence of E. coli, Salmonella, copper, nickel, zinc, and manganese in irrigation water, lettuce leaves, and agricultural soil in the Litani River Basin (LRB), Lebanon.

METHOD

Samples were collected from five demonstration plots employing different agricultural practices. Heavy metal concentrations were determined using atomic absorption spectrometry, while E. coli and Salmonella testing were conducted through conventional culturing techniques. The impact of E. coli contamination on seed germination and the interaction effects between E. coli and heavy metals were also examined. The study also compared the effectiveness of various irrigation systems in reducing bacterial contamination.

RESULTS

The results demonstrated that contamination levels varied significantly across the plots and irrigation types. This variation underscores the necessity of site-specific mitigation strategies to enhance food safety. Our findings highlight the importance of selecting appropriate irrigation methods and implementing tailored agricultural practices to minimize the risk of contamination.

CONCLUSION

This research provides valuable insights for optimizing agricultural practices in the LRB to ensure food safety and environmental sustainability.

Assessing the mediating role of iron status on associations between an industry-relevant metal mixture and verbal learning and memory in Italian adolescents

BACKGROUND

Metals, including lead (Pb), manganese (Mn), chromium (Cr) and copper (Cu), have been associated with neurodevelopment; iron (Fe) plays a role in the metabolism and neurotoxicity of metals, suggesting Fe may mediate metal-neurodevelopment associations. However, no study to date has examined Fe as a mediator of the association between metal mixtures and neurodevelopment.

OBJECTIVE

We assessed Fe status as a mediator of a mixture of Pb, Mn, Cr and Cu in relation to verbal learning and memory in a cohort of Italian adolescents.

METHODS

We used cross-sectional data from 383 adolescents (10-14 years) in the Public Health Impact of Metals Exposure Study. Metals were quantified in blood (Pb) or hair (Mn, Cr, Cu) using ICP-MS, and three markers of Fe status (blood hemoglobin, serum ferritin and transferrin) were quantified using luminescence assays or immunoassays. Verbal learning and memory were assessed using the California Verbal Learning Test for Children (CVLT-C). We used Bayesian Kernel Machine Regression Causal Mediation Analysis to estimate four mediation effects: the natural direct effect (NDE), natural indirect effect (NIE), controlled direct effect (CDE) and total effect (TE). Beta (β) coefficients and 95 % credible intervals (CIs) were estimated for all effects.

RESULTS

The metal mixture was jointly associated with a greater number of words recalled on the CVLT-C, but these associations were not mediated by Fe status. For example, when ferritin was considered as the mediator, the NIE for long delay free recall was null (β = 0.00; 95 % CI = -0.22, 0.23). Conversely, the NDE (β = 0.23; 95 % CI = 0.01, 0.44) indicated a beneficial association of the mixture with recall that operated independently of Fe status.

CONCLUSION

An industry-relevant metal mixture was associated with learning and memory, but there was no evidence of mediation by Fe status. Further studies in populations with Fe deficiency and greater variation in metal exposure are warranted.

Manganese-Induced Parkinsonism: Evidence from Epidemiological and Experimental Studies

Manganese (Mn) exposure has evolved from acute, high-level exposure causing manganism to low, chronic lifetime exposure. In this latter scenario, the target areas extend beyond the globus pallidus (as seen with manganism) to the entire basal ganglia, including the substantia nigra pars compacta. This change of exposure paradigm has prompted numerous epidemiological investigations of the occurrence of Parkinson's disease (PD), or parkinsonism, due to the long-term impact of Mn. In parallel, experimental research has focused on the underlying pathogenic mechanisms of Mn and its interactions with genetic susceptibility. In this review, we provide evidence from both types of studies, with the aim to link the epidemiological data with the potential mechanistic interpretation.

Bioelectricity Production from Microbial Fuel Cell (MFC) Using Lysinibacillus xylanilyticus Strain nbpp1 as a Biocatalyst

Microbial fuel cells (MFCs) function by using microorganisms to decompose the substrate at the anode, producing electrons and protons. These charges are then transported to the cathode, where electricity is generated. Previous studies have shown their promising probabilities for practical applications. MFCs are praised for their ability to address energy shortages and environmental pollution simultaneously. They have the potential to generate electricity directly from organic substances, reducing energy losses that occur during intermediate conversion steps. The main challenge lies in transitioning these technologies from the laboratory setting to practical systems that can be implemented on a large scale for bioenergy production along with various engineering hurdles. This study focused on investigating the power production potential of a soil-isolated bacterial strain taxonomically classified as Lysinibacillus xylanilyticus nbpp1, which is a relatively new addition to the extensive range of biocatalysts known for their ability to generate electricity. The study analyzed the electrochemical performance of an H-type MFC setup. LB broth was used as the substrate, while aluminum and graphite served as electrode materials. Other parameters, such as Coulombic efficiency, internal resistance, and electrode corrosion rate, were also measured. The MFC produced a high open circuit voltage of 1127 mV and achieved a maximum power density of 6.71 mW/cm² at a current density of 11.14 mA/cm². The MFC setup successfully powered LED lamps when connected in a joint circuit, showcasing its potential for practical applications. These findings suggest the promising high electrochemical performance of the MFC system in terms of electricity generation using the specified conditions.

Accumulation of heavy metals and human health risk assessment of vegetable consumption from a farm within the Korle lagoon catchment

The Korle lagoon is known to have high concentration of heavy metals. The use of land for agriculture and water for irrigation within the Korle Lagoon's catchment constitutes a potential health risk. Due to this, the study assessed the concentration of heavy metals in some vegetables (Amaranth, Spinach, Eggplant, Lettuce, Cauliflower, and Onion) and their corresponding soil from a farm within the Korle Lagoon's catchment. The estimated daily intake (EDI), hazard quotient (HQ), and lifetime cancer risk (LCR) was used to assess their health risks. Among the vegetables tested, heavy metals in lettuce exceeded their recommended guideline level. Additionally, the concentrations of Fe (265.94-3599.60 mg/kg) and Zn (76.77-294.70 mg/kg) in all vegetables were above the recommended guideline level. Also, Zn (227.30-534.57 mg/kg) and Pb (101.53-407.58 mg/kg), in soil were above the recommended guideline level for soil. The results also showed not only the severity of heavy metal pollution of soil in the study area, but also risks that were deemed carcinogenic and noncarcinogenic to both adults and children as a result of consumption of vegetables from the study area. The hazard index for adults (0.46-41.156) and children (3.880-384.122), were high for all vegetables tested and are associated with cancer risk due to high Cr and Pb levels. The risk assessment showed that children may suffer more carcinogenic and noncarcinogenic health risk than adults. The study concluded that vegetables grown within the Korle lagoon's catchment is not suitable for consumption due to the associated adverse health effect.

A Multi-Method Approach for Impact Assessment of Some Heavy Metals on Lactuca sativa L

Heavy metals represent a large category of pollutants. Heavy metals are the focus of researchers around the world, mainly due to their harmful effects on plants. In this paper, the influence of copper, cadmium, manganese, nickel, zinc and lead, present in soil in different concentrations (below the permissible limit, the maximum permissible concentration and a concentration higher than the maximum permissible limit) on lettuce (Lactuca sativa L.) was evaluated. For this purpose, the authors analyzed the variation of photosynthetic pigments, total polyphenols, antioxidant activity and the elemental content in the studied plants. The experimental results showed that the variation of the content of biologically active compounds, elemental content and the antioxidant activity in the plants grown in contaminated soil, compared to the control plants, depends on the type and concentration of the metal added to the soil. The biggest decrease was recorded for plants grown in soil treated with Ni I (-42.38%) for chlorophyll a, Zn II (-32.92%) for chlorophyll b, Ni I (-40.46%) for carotenoids, Pb I (-40.95%) for polyphenols and Cu III (-29.42%) for DPPH. On the other hand, the largest increase regarding the amount of biologically active compounds was registered for Mn I (88.24%) in the case of the chlorophyll a, Mn I (65.56%) for chlorophyll b, Pb I (116.03%) for carotenoids, Ni III (1351.23%) for polyphenols and Ni III (1149.35%) for DPPH.

Relationships of Nutritional Factors and Agrochemical Exposure with Parkinson's Disease in the Province of Brescia, Italy

Environmental exposures to agrochemicals and nutritional factors may be associated with Parkinson's Disease (PD). None of the studies to date has examined the combined effects of diet and agricultural chemical exposure together. To address these research gaps, we aimed to assess the association of nutritional factors and agrochemical exposure with the risk of PD. A hospital-based case-control study was conducted. Multivariable logistic regressions were used to estimate the association of nutritional and agrochemical exposures with PD, adjusting for gender, age, socio-economic status, head injury, family history, smoking, metals exposure, and α-synuclein gene polymorphism. Weighted Quantile Sum (WQS) regression was applied to examine the effect of dietary components as a mixture. We recruited 347 cases and 389 controls. Parent history of PD (OR = 4.15, 95%CI: 2.10, 8.20), metals exposure (OR = 2.50, 95%CI: 1.61-3.89), SNCA rs356219 polymorphism (OR = 1.39, 95%CI: 1.04-1.87 for TC vs. TT; OR = 2.17, 95%CI: 1.43-3.28 for CC vs. TT), agrochemical exposures (OR = 2.11, 95%CI: 1.41-3.16), and being born in the Brescia province (OR = 1.83, 95%CI: 1.17-2.90) were significantly associated with PD. Conversely, fish intake and coffee consumption had a protective effect. The study confirmed the role of environmental exposures in the genesis of PD. Fish intake and coffee consumption are protective factors even when agricultural chemical exposures exist. Genetic factors and metals exposure were confirmed as risk factors for PD.

Critical windows of susceptibility in the association between manganese and neurocognition in Italian adolescents living near ferro-manganese industry

INTRODUCTION

Understanding the neurodevelopmental effects of manganese (Mn) is complicated due to its essentiality for growth and development. While evidence exists for the harmful effects of excess Mn, pediatric epidemiologic studies have observed inconsistent associations between Mn and child cognition.

OBJECTIVE

We sought to estimate prospective associations between Mn measured in three different early-life time windows with adolescent cognition using deciduous teeth biomarkers.

METHODS

Deciduous teeth were collected from 195 participants (ages 10-14 years) of the Public Health Impact of Manganese Exposure (PHIME) study in Brescia, Italy. Measurements of tooth Mn represented prenatal (∼14 weeks gestation - birth), early postnatal (birth - 1.5 years) and childhood (∼1.5 - 6 years) time windows. Neuropsychologists administered the Wechsler Intelligence Scale for Children, 3rd edition (WISC-III), to obtain composite IQ and subtest scores. Associations between tooth Mn at each time window and adolescent WISC-III scores were estimated using multivariable linear regression. We tested differences in associations between Mn and outcomes across time windows using multiple informant models. Sex-specific associations were explored in stratified models.

RESULTS

Adjusted associations between tooth Mn and composite IQ scores were positive in the prenatal period and negative in the childhood period. Associations were strongest for subtest scores that reflect working memory, problem solving, visuospatial ability and attention: prenatal Mn was positively associated with Digits backward [SD change in score per interquartile range increase in Mn: β = 0.20 (95 % CI: 0.02, 0.38)] and Block design [β = 0.21 (0.01, 0.41)] and early postnatal Mn was positively associated with Digits forward [β = 0.24 (0.09, 0.40)], while childhood Mn was negatively associated with Coding [β = -0.14 (-0.28, -0.001)]. Sex-stratified analyses suggested different Mn-cognition associations for boys and girls and was also dependent on the time window of exposure.

CONCLUSION

Our results suggest that exposure timing is critical when evaluating Mn associations between Mn and cognition. Higher prenatal Mn was beneficial for adolescent cognition; however, these beneficial associations shifted towards harmful effects in later time windows. Cognitive domains most sensitive to Mn across time windows included visuospatial ability, working memory, attention and problem-solving.

Metal Exposure and SNCA rs356219 Polymorphism Associated With Parkinson Disease and Parkinsonism

Objective: In the province of Brescia, Italy, historical neurotoxic metal exposure has occurred for several decades. This study aimed to explore the role of metal exposure and genetics on Parkinson's Disease (PD) and Parkinsonism. Methods: Cases were enrolled from four local clinics for movement disorders. Randomly selected controls non-affected by neurological or psychiatric conditions were enrolled from the same health centers keeping a similar gender ratio and age distribution as for cases. Data on sociodemographic variables, clinical onset and life habits were collected besides accurate occupational and residential history. Blood samples were collected from all participants for genotyping of target polymorphisms in genes linked to PD and/or metal transport. Results: A total number of 432 cases and 444 controls were enrolled in the study, with average age of 71 years (72.2 for cases and 70 for controls). The average age at diagnosis was 65.9 years (SD 9.9). Among the potential risk factors, family history of PD or Parkinsonism showed the strongest association with the diseases (OR = 4.2, 95% CI 2.3, 7.6 on PD; OR = 4.3, 95% CI 1.9, 9.5 for Parkinsonism), followed by polymorphism rs356219 in the alpha-synuclein (SNCA) gene (OR = 2.03, 95% CI 1.3, 3.3 for CC vs. TT on PD; OR = 2.5, 95% CI 1.1, 5.3 for CC vs. TT on Parkinsonism), exposure to metals (OR = 2.4;, 95% CI 1.3, 4.2 on PD), being born in a farm (OR = 1.8; 95% CI 1.1, 2.8 on PD; OR = 2.6; 95% CI 1.4, 4.9 on Parkinsonism) and being born in the province of Brescia (OR = 1.7; 95% CI 1.0, 2.9 on PD). Conditional OR of having PD depending by SNCA polymorphism and metal exposure highlights higher risk of PD among CC SNCA carriers and being exposed to metals. However, the interaction term was not statistically significant. Conclusions: Lifetime exposure to metals and genetic variation in SNCA gene are relevant determinants of PD and Parkinsonism in the highly industrialized area of Brescia, Italy. The lack of evidence of statistical interaction between environmental and genetic factors may be due to the low frequencies of subjects representing the exposure categories and the polymorphism variants and does not rule out the biological interaction.

Enrichment, Source Apportionment and Health Risk Assessment of Soil Potentially Harmful Elements Associated with Different Land Use in Coastal Tidelands Reclamation Area, Eastern China

Coastal tidelands are important ecological habitat resources and valuable resources for agricultural land reclamation. Enrichment of potentially harmful elements (PHEs) in soil caused by anthropogenic activity is an important factor implicated in the ecological deterioration of soil in China. A total of 54 soil sample sites were selected from a 30-year reclaimed tideland and an adjoining coastal wetland. Descriptive and multivariate statistical analyses were performed to describe the enrichment, source, health risk status of eight PHEs (As, Co, Cr, Cu, Mn, Ni, Pb, and Zn) after long-term reclamation. Results indicated that after 30 years of reclamation, most soil PHEs are slightly enriched, whereas no serious threat of environmental pollution was observed. In the reclamation area, the enrichment of PHEs in the aquaculture land, industrial land, and cropland was relatively high compared with other land use types, such as tideland and halophyte land. The source analysis divided the PHEs into five categories: (1) Cu; (2) Co and Mn; (3) Cr; (4) As and Pb; (5) Zn and Ni. Cu was completely derived from natural parent materials and other elements were governed by both weathering of parent rock and human activities, including agricultural activities, industrial production, and transportation emissions. The health risk assessment showed that the soil PHEs potentially had no non-carcinogenic risk to the public, but there was an acceptable probability to have cancer due to Cr and As. Meanwhile, children are more susceptible to harm from the PHEs in soil than adults. According to the economic and social development situation in the coastal region, it is necessary to pay attention to the environmental threats of PHEs enrichment.

Effect of 24-epibrassinolide on reactive oxygen species and antioxidative defense systems in tall fescue plants under lead stress

Lead is one of the most hazardous pollutants to both the environment as well as human beings. As one of the approaches to enhance phytoremediation, brassinosteroids are predicted as a potential candidate phytohormone for assisted phytoremediation. Few studies have focused on the physiological regulations of tall fescue plants (Festuca arundinacea Schreb.), a potential phytoremediation species, for its responses to applications of brassinosteroids under lead stress. Therefore, the objectives of this study were to investigate the effects of foliar application of 24-epibrassinolide, a brassinosteroids analogue, on reactive oxygen species accumulation and antioxidative defense systems of tall fescue when exposed to lead, and ultimately its potential to be used in phytoremediation. When exposed to lead (1000 mg/kg) for 80 d, decreases in shoot and root biomass of tall fescue biomass as well as chlorophyll and carotenoid productions were found. Foliar application of 24-epibrassinolide at three rates and five applications every 7 d improved the biomass of both shoots and roots, and increased the photosynthetic pigments. The improved lead tolerance in tall fescue plants after 24-epibrassinolide applications was associated with reduced H₂O₂ and O₂^.- accumulations and increased antioxidative enzyme activities including superoxide dismutase, catalase, and guaiacol peroxidase. Additionally, osmoprotectants increased and lipid peroxidation decreased. Ultimately, foliar applications of 24-epibrassinolide enhanced the lead recovery rate of tall fescue plants, proving its potential role in phytoremediation for soil contaminated with heavy metals such as lead.

Association between heavy metals and metalloids in topsoil and mental health in the adult population of Spain

BACKGROUND AND OBJECTIVES

Despite the biological plausibility of the association between heavy metal exposure and mental health disorders, epidemiological evidence remains scarce. The objective was to estimate the association between heavy metals and metalloids in soil and the prevalence of mental disorders in the adult population of Spain.

METHODS

Individual data came from the Spanish National Health Survey 2011-2012, 18,073 individuals residing in 1772 census sections. Mental health was measured with the 12-item General Health Questionnaire. The concentration estimates of heavy metal and metalloid levels in topsoil (upper soil horizon) came from the Geochemical Atlas of Spain based on 13,317 soil samples. Levels of lead (Pb), arsenic (As), cadmium (Cd) and manganese (Mn) were estimated in each census section by "ordinary Kriging". Odds ratios (OR) were calculated by multilevel logistic regression models.

RESULTS

Compared with the lowest Pb concentration levels quartile, the OR for the second quartile was 1.29 (95%CI: 1.11-1.50), increasing progressively to 1.37 (95%CI: 1.17-1.60) and 1.51 (95%CI: 1.27-1.79) in the third and fourth quartiles, respectively. For As, the association was observed in the third and fourth quartiles: 1.21 (95%CI: 1.04-1.41) and 1.42 (95% CI: 1.21-1.65), respectively. Cd was associated also following a gradient from the second quartile: 1.34 (95%CI: 1.15-1.57) through the fourth: 1.84 (95%CI: 1.56-2.15). In contrast, Mn only showed a positive association at the second quartile. Additionally, individuals consuming vegetables > once a day the OR for the fourth quartile of Pb concentration, vs. the first, increased to 2.93 (95%CI: 1.97-4.36); similarly for As: 3.00 (95%CI: 2.08-4.31), and for Cd: 3.49 (95%CI: 2.33-5.22).

CONCLUSIONS

Living in areas with a higher concentration of heavy metals and metalloids in soil was associated with an increased probability of having a mental disorder. These relationships were strengthened in individuals reporting consuming vegetables > once a day.

Manganese and Developmental Neurotoxicity

Manganese (Mn) is an essential metal that plays a fundamental role for brain development and functioning. Environmental exposure to Mn may lead to accumulation in the basal ganglia and development of Parkinson-like disorders. The most recent research is focusing on early-life overexposure to Mn and the potential vulnerability of younger individuals to Mn toxicity also in regard to cognitive and executive functions through the involvement of the frontal cortex.Neurodevelopmental disturbances are increasing in the society, and understanding the potential role of environmental determinants is a key for prevention. Therefore, assessing the environmental sources of Mn exposure and the mechanisms of developmental neurotoxicity and defining appropriate biomarkers of exposure and early functional alterations represent key issues to improve and address preventive strategies. These themes will be reviewed in this chapter.

Effects of co-cropping Bidens pilosa (L.) and Tagetes minuta (L.) on bioaccumulation of Pb in Lactuca sativa (L.) growing in polluted agricultural soils

Polluted agricultural soils are a serious problem for food safety, with phytoremediation being the most favorable alternative from the environmental perspective. However, this methodology is generally time-consuming and requires the cessation of agriculture. Therefore, the purpose of this study was to evaluate two potential phytoextractor plants (the native species Bidens pilosa and Tagetes minuta) co-cropped with lettuce growing on agricultural lead-polluted soils. The concentrations of Pb, as well as of other metals, were investigated in the phytoextractors, crop species, and in soils, with the potential risk to the health of consumers being estimated. The soil parameters pH, EC, organic matter percentage and bioavailable lead showed a direct relationship with the accumulation of Pb in roots. In addition, the concentration of Pb in roots of native species was closely related to Fe (B. pilosa, r = 0.81; T. minuta r = 0.75), Cu (T. minuta, r = 0.93), Mn (B. pilosa, r = 0.89) and Zn (B. pilosa, r = 0.91; T. minuta, r = 0.91). Our results indicate that the interaction between rhizospheres increased the phytoextraction of lead, which was accompanied by an increase in the biomass of the phytoextractor species. However, the consumption of lettuce still revealed a toxicological risk from Pb in all treatments.

Metal contamination of home garden soils and cultivated vegetables in the province of Brescia, Italy: implications for human exposure

BACKGROUND

For the past century, ferroalloy industries in Brescia province, Italy produced particulate emissions enriched in manganese (Mn), lead (Pb), zinc (Zn), copper (Cu), cadmium (Cd), chromium (Cr), iron (Fe), and aluminum (Al). This study assessed metal concentrations in soil and vegetables of regions with varying ferroalloy industrial activity levels.

METHODS

Home gardens (n=63) were selected in three regions of varying ferroalloy plant activity durations in Brescia province. Total soil metal concentration and extractability were measured by X-Ray Fluorescence (XRF), aqua regia extraction, and modified Community Bureau of Reference (BCR) sequential extraction. Unwashed and washed spinach and turnips cultivated in the same gardens were analyzed for metal concentrations by flame atomic absorption spectrometry.

RESULTS

Median soil Al, Cd, Fe, Mn, Pb, and Zn concentrations were significantly higher in home gardens near ferroalloy plants compared to reference home gardens. The BCR method yielded the most mobile soil fraction (the sum of extractable metals in Fractions 1 and 2) and all metal concentrations were higher in ferroalloy plant areas. Unwashed spinach showed higher metal concentrations compared to washed spinach. However, some metals in washed spinach were higher in the reference area likely due to history of agricultural product use. Over 60% of spinach samples exceeded the 2- to 4-fold Commission of European Communities and Codex Alimentarius Commission maximum Pb concentrations, and 10% of the same spinach samples exceeded 2- to 3-fold maximum Cd concentrations set by both organizations. Turnip metal concentrations were below maximum standard reference values.

CONCLUSIONS

Prolonged industrial emissions increase median metal concentrations and most soluble fractions (BCR F1+F2) in home garden soils near ferroalloy plants. Areas near ferroalloy plant sites had spinach Cd and Pb metal concentrations several-fold above maximum standard references. We recommend thorough washing of vegetables to minimize metal exposure.

Neurofunctional dopaminergic impairment in elderly after lifetime exposure to manganese

BACKGROUND

Manganese (Mn) is an essential element that can become neurotoxic through various exposure windows over the lifespan. While there is clear evidence of Mn neurotoxicity in pediatric and adult occupational populations, little is known about effects in the elderly who may exhibit enhanced susceptibilities due to compromised physiology compared to younger adults. In the province of Brescia, Italy, the Valcamonica area has been the site of three ferroalloy plants operating from 1902 to 2001. Metal emissions of Mn and to a lesser extent lead (Pb) have impacted the surrounding environment, where a high prevalence of Parkinsonism was previously observed. This study aimed to assess neurocognitive and motor functions in healthy elderly subjects residing for most of their lifetime in Valcamonica or in a reference area unimpacted by ferroalloy plant activity.

METHODS

Subjects were enrolled for extensive neurobehavioral assessment of motor, cognitive and sensory functions. Exposure was assessed with 24h personal air sampling for PM10 airborne particles, surface soil and tap water measurement at individual households, Mn levels in blood and urine and Pb in blood. Dose-response relationships between exposure indicators and biomarkers and health outcomes were analyzed with generalized (linear and logistic) additive models (GAM).

RESULTS

A total of 255 subjects (55% women) were examined; most (52.9%) were within the 65-70 years age class. Average airborne Mn was 26.41 ng/m(3) (median 18.42) in Valcamonica and 20.96 ng/m(3) (median 17.62) in the reference area. Average Mn in surface soil was 1026 ppm (median 923) in Valcamonica and 421 ppm (median 410) in the reference area. Manganese in drinking water was below the LDL of 1 μg/L. The GAM analysis showed significant association between airborne Mn (p=0.0237) and the motor coordination tests of the Luria Nebraska Neuropsychological Battery. The calculation of the Benchmark Dose using this dose-response relationship yielded a lower level confidence interval of 22.7 ng/m(3) (median 26.4). For the odor identification score of the Sniffin Stick test, an association was observed with soil Mn (p=0.0006) and with a significant interaction with blood Pb (p=0.0856). Significant dose-responses resulted also for the Raven's Colored Progressive Matrices with the distance from exposure point source (p=0.0025) and Mn in soil (p=0.09), and for the Trail Making test, with urinary Mn (p=0.0074). Serum prolactin (PRL) levels were associated with air (p=0.061) and urinary (p=0.003) Mn, and with blood Pb (p=0.0303). In most of these associations age played a significant role as an effect modifier.

CONCLUSION

Lifelong exposure to Mn was significantly associated with changes in odor discrimination, motor coordination, cognitive abilities and serum PRL levels. These effects are consistent with the hypothesis of a specific mechanism of toxicity of Mn on the dopaminergic system. Lead co-exposure, even at very low levels, can further enhance Mn toxicity.