What is vanadium
Vanadium is a metallic element with the atomic symbol V, atomic number 23, and atomic weight 50.94. Constituting 0.015% of the earth’s crust, vanadium is almost as abundant as zinc 1). Vanadium is omnipresent in the biosphere, another precondition for general availability for living organisms. Vanadium is the second most abundant transition element in seawater (45 nM or nanomolar), only below to molybdenum (100 nM) and more abundant than iron (0.02-1 nM) 2). Vanadium is used in the manufacture of vanadium steel 3). Prolonged exposure can lead to chronic intoxication caused by absorption usually via the lungs. Vanadium is a trace element that exists in multiple oxidation states and forms complexes with proteins. Vanadium has not been shown to be an essential element and indeed, is absorbed poorly. No deficiency state of vanadium has been demonstrated in humans 4). High doses of vanadium are toxic to animals and can cause neurologic, hematologic, renal and hepatic toxicity. Feeding of high doses to humans causes gastrointestinal upset, but vanadium has not been linked to hepatotoxicity due to dietary intake or environmental exposures in humans 5).
Vanadium is present in the human body tissues in smallest concentrations around 60 nM 6). Vanadium daily intake comes from eating food, drinking water, polluted air or industrially prepared nutrition supplements 7). Vanadium presence in the human body seems not to be essential and vanadium bearing coenzymes or enzymes have not been identified. Vanadium presence seems more a matter of tolerance. Vanadate (H2VO4ˉ in oxidation state +5) geometrically resembles the ubiquitous biological messenger phosphate (H2PO4ˉ or HPO42ˉ in formal state +5). The charges and structural match may explain its physiological role in analogy to phosphate ions in biochemical reactions 8). There is no strong evidence that supplements of the trace mineral vanadium improve blood sugar control in people with type 2 diabetes 9).
Vanadium has been suggested to have fetotoxicity and developmental toxicity in animal studies, and epidemiological studies have reported an association between a decrease in birthweight and vanadium exposure estimated from particulate matter 10). The results of this study 11) can enrich the biological monitoring data on urinary vanadium in pregnant women; and may be evidence that vanadium may affect fetal development.
Vanadium can cross the placental barrier, so the fetus is exposed and vanadium accumulates in the fetal skeleton 12). Animal studies have shown that exposure to vanadium during pregnancy induces reproductive toxic effects 13) and affects the development and behavior of offspring 14). In previous epidemiological studies, vanadium, as an oil-combustion-associated elemental constituent in air-borne particulate matter (PM2.5), has been found to be associated with a reduction in birthweight 15). Moreover, Bell et al. 16) analyzed the effect of exposure to PM2.5 vanadium during trimesters and found that the most significant association with reduced birthweight was observed during the third trimester. Low birthweight (LBW, <2500 g) continues to be a significant public health problem globally UNICEF 2009 17). An increasing number of studies have suggested that exposure to environmental heavy metals, such as arsenic, lead and cadmium, during pregnancy is a risk factor for low birthweight 18). A urinary vanadium concentration is considered as a biological indicator of exposure to vanadium 19). In this study, scientists conducted a nested case–control study in the province of Hubei, China to investigate the relationship between maternal urinary vanadium concentrations and the odds of delivering low birthweight infants.
The maternal urine samples were collected before labor (the median gestational age was 39 weeks, range 27–42 weeks) and stored in polypropylene tubes at −20°C until analysis. The frozen urine samples were thawed at room temperature, and then 1 ml of the urine sample (or reference standard) and 4 ml of 3% v/v HNO3 were added to a polypropylene tube for overnight nitrification and were further digested by ultrasound at 40°C for 1 h. The vanadium concentrations in the urine were measured by inductively coupled plasma mass spectrometry. The standard Reference Material Human Urine (SRM2670a Toxic Elements in Urine, National Institute of Standards and Technology, USA) was used as an external quality control in each batch to assess the instrument performance. The limit of detection for vanadium was 0.002 µg/l. The urinary vanadium concentrations in the Chinese study population were all above the limit of detection. The recovery of the quality control standard by using this procedure was 90%. The intra-day coefficient of variation (CV) was 1.57%, and the inter-day CV was 4.16%. Arsenic, lead, cadmium and nickel were measured simultaneously, and the detection rate of these metals was higher than 98%.
Urinary creatinine concentrations were measured to adjust for variability in the dilution of the urine and were determined by a creatinine kit. The vanadium concentration in the urine was reported as a ratio of the vanadium level to the creatinine level (μg/g creatinine).
Potential covariates were included in the models based on biologic plausibility or if they altered the parameter estimate of the main effect by more than 10%. Smoking and alcohol consumption during pregnancy were not included because few women smoke or drink during pregnancy in China 20), and there was only one woman who reported smoking and three women who reported drinking among the study participants. Previous studies suggested that gestational age is a major contributor to birthweight and should be considered a strong confounder when investigating associations with birthweight 21).
Table 1. Basic characteristics of the study population and urinary concentrations of vanadium in different demographic categories (μg/g creatinine).
| Characteristics | Cases (n = 204) | Controls (n = 612) | ||
|---|---|---|---|---|
| N (%) | Median (IQR) Vanadium (μg/g creatinine) | N (%) | Median (IQR) Vanadium (μg/g creatinine) | |
| Total | 204 | 3.04 (1.76–5.77) | 612 | 1.93 (1.19–4.28) |
| Infant gender | ||||
| Male | 101 (49.5) | 3.29 (1.74–8.17) | 303 (49.5) | 2.08 (1.31–5.61) |
| Female | 103 (50.5) | 3.01 (1.76–4.95) | 309 (50.5) | 1.77 (1.09–3.45) |
| Maternal age | ||||
| <24 years | 33 (16.2) | 2.57 (1.67–5.48) | 95 (15.5) | 2.34 (1.30–5.27) |
| 24–34 years | 154 (75.5) | 3.28 (1.77–5.87) | 467 (76.3) | 1.85 (1.14–3.95) |
| ≥35 years | 17 (8.3) | 2.21 (1.84–4.72) | 50 (8.2) | 2.07 (1.35–6.10) |
| Education | ||||
| Less than high school | 89 (43.6) | 2.69 (1.68–5.04) | 167 (27.3) | 2.29 (1.26–5.55) |
| High school | 38 (18.6) | 3.13 (1.31–9.58) | 120 (19.6) | 2.02 (1.24–4.83) |
| College and above | 77 (37.8) | 3.54 (1.98–5.78) | 322 (52.6) | 1.81 (1.14–3.54) |
| Missing | 0 (0.0) | / | 3 (0.5) | 1.28 (1.26–8.25) |
| Household income | ||||
| <50 000 Yuan per year | 116 (56.9) | 3.04 (1.76–5.47) | 275 (44.9) | 1.93 (1.19–3.79) |
| ≥50 000 Yuan per year | 61 (29.9) | 3.37 (1.81–9.18) | 279 (45.6) | 1.77 (1.12–3.99) |
| Missing | 27 (13.2) | 2.67 (1.32–4.51) | 58 (9.5) | 3.11 (1.63–7.13) |
| Parity | ||||
| 1 | 159 (77.9) | 3.09 (1.74–5.78) | 501 (81.9) | 1.97 (1.22–4.26) |
| ≥2 | 45 (22.1) | 2.61 (1.84–5.48) | 111 (18.1) | 1.69 (0.99–4.54) |
| Pre-pregnancy BMI | ||||
| Underweight (<18.5 kg/m2) | 60 (29.4) | 3.39 (1.60–8.31) | 125 (20.4) | 1.97 (1.24–4.88) |
| Normal (18.5–23.9 kg/m2) | 108 (52.9) | 3.31 (1.91–5.33) | 385 (62.9) | 1.93 (1.17–4.98) |
| Overweight (≥24 kg/m2) | 26 (12.8) | 2.00 (1.23–4.42) | 85 (13.9) | 1.78 (1.31–2.54) |
| Missing | 10 (4.9) | 2.42 (1.95–6.05) | 17 (2.8) | 2.02 (1.21–5.27) |
| Gestational weight gaina | ||||
| <14 kg | 83 (40.7) | 2.92 (1.62–4.72) | 145 (23.7) | 2.14 (1.43–4.60) |
| 14–19 kg | 66 (32.3) | 3.43 (1.89–5.58) | 269 (44.0) | 1.79 (1.15–3.65) |
| >19 kg | 46 (22.6) | 3.12 (1.81–10.54) | 183 (30.0) | 2.00 (1.15–6.07) |
| Missing | 9 (4.4) | 4.10 (1.95–7.69) | 15 (2.5) | 1.94 (1.24–3.40) |
| Passive smoking during pregnancy | ||||
| Yes | 47 (23.0) | 3.09 (1.76–9.84) | 129 (21.1) | 2.12 (1.41–5.25) |
| No | 149 (73.0) | 3.24 (1.76–5.35) | 464 (75.8) | 1.91 (1.16–4.11) |
| Missing | 8 (3.9) | 1.99 (1.74–2.77) | 19 (3.1) | 1.78 (0.94–7.13) |
| Gestational age | ||||
| <37 weeks | 108 (52.9) | 3.59 (1.79,5.92) | 14 (2.3) | 6.05 (2.52–7.66) |
| ≥37 weeks | 96 (47.1) | 2.74 (1.68–5.55) | 598 (97.7) | 1.91 (1.19–4.14) |
Footnotes: IQR = interquartile range.
aGestational weight gain was categorized into three levels based on the tertile distribution of the weight gain in the whole study population.
Relationship between maternal vanadium exposure and low birthweight
Table 2 illustrates the relationship between maternal urinary vanadium levels and the odds of low birthweight. After adjusting for potential confounders, a significant positive trend was observed between low birthweight and increasing levels of maternal urinary vanadium concentrations relative to the lowest tertile [adjusted OR = 1.69 for the medium tertile; adjusted OR = 2.23 for the highest tertile]. The researchers also performed an analysis that excluded preterm births (96 pairs of case and control were included), and an adjusted OR of 2.15 was still observed for low birthweight in the medium tertile of vanadium and 2.40 for the highest tertile of term infants.
This study 23) is the first to examine the association between maternal urinary vanadium concentrations and infant low birthweight. The researchers found that higher levels of maternal urinary vanadium were associated with increased odds of delivering low birthweight infants. Specifically, compared with mothers in the lowest tertile (≤1.42 μg/g creatinine), mothers in the highest tertile (≥2.91 μg/g creatinine) and medium tertile of urinary vanadium levels had 2.23 and 1.69 times the likelihood of delivering low birthweight infants, respectively. Additionally, the association was not modified by maternal age and infant gender. As the causes of low birthweight in preterm and full-term births may be different 24), the study authors also conducted a sensitivity analysis excluding preterm births, but they still observed a positive association between maternal urinary vanadium and low birthweight in term infants.
In the same study, scientists found that maternal urinary vanadium concentrations were positively related to the odds of infant low birthweight. Several previous epidemiologic studies examined the association between vanadium exposure estimated from PM2.5 during pregnancy and infant birthweight and found that vanadium in PM2.5 was associated with reduced birthweight. A study conducted in four cities in Connecticut and Massachusetts, USA reported that exposure to an interquartile range (IQR, 0.004 μg/m³) increase in PM2.5 vanadium concentrations was associated with a 5 g decrease in birthweight, and the exposure that occurred in the third trimester showed the most significant effect 25), indicating that the third trimester may be the window period of vanadium exposure for the fetus. Basu et al. 26) also found a significant association between exposure to PM2.5 vanadium during pregnancy and a reduction in birthweight among residents in California. However, another study conducted in the north-eastern and mid-Atlantic USA by Ebisu and Bell 27) did not observe these effects. The inconsistent results may be attributed to differences in study design and to diverse vanadium levels in PM2.5.
Biological mechanisms explaining the impact of vanadium on birthweight are not clear. Vanadium is reported to be a potent inhibitor of DNA and protein synthesis and is able to affect several metabolic processes 28), which may lead to fetal intrauterine growth restriction after the vanadium compounds transfer from the mother to the fetus through the placenta. Additionally, some evidence suggested that vanadium triggers oxidative stress 29), and increased oxidative stress in uteroplacental tissues may influence placental maternal–fetal connection and affect fetal growth and development 30).
Exposure to arsenic, lead and cadmium have also been reported to be associated with decreased birthweight 31). Nickel has been explored together with vanadium as an indicator for oil combustion sources in PM2.5 32) and reported to be associated with term low birthweight 33).
Table 2. Odds Ratio of low birthweight associated with the levels of vanadium in maternal urine.
| Vanadium (µg/g creatinine) | Cases | Controls | ORa (95% CI) | ORb (95% CI) |
|---|---|---|---|---|
| Total (n = 816) | ||||
| ≤1.42 | 39 | 204 | 1 | 1 |
| 1.42–2.91 | 56 | 204 | 1.43 (0.90, 2.26) | 1.69 (0.92, 3.10) |
| ≥2.91 | 109 | 204 | 2.95 (1.93, 4.51) | 2.23 (1.23, 4.05) |
| P for trend | <0.01 | 0.02 | ||
| Excluding preterm births (n = 384) | ||||
| ≤1.43 | 19 | 96 | 1 | 1 |
| 1.43–3.10 | 35 | 96 | 1.89 (1.00, 3.54) | 2.15 (1.07, 4.34) |
| ≥3.10 | 42 | 96 | 2.46 (1.27, 4.74) | 2.40 (1.16, 4.97) |
| P for trend | 0.02 | 0.07 | ||
Footnotes: Gestational age was not adjusted after excluding preterm births.
Abbreviations: OR = odds ratio; CI = confidence interval.
aUnadjusted odds ratio.
bAdjusted for gestational age, education, pre-pregnancy body mass index, parity and passive smoking during pregnancy.
Where is vanadium found?
Vanadium is a compound that occurs in nature as a white-to-gray metal, and is often found as crystals 35). Pure vanadium has no smell. Vanadium usually combines with other elements such as oxygen, sodium, sulfur, or chloride. Vanadium and vanadium compounds can be found in the earth’s crust and in rocks, some iron ores, and crude petroleum deposits 36). Vanadium is mostly combined with other metals to make special metal mixtures called alloys 37). Vanadium in the form of vanadium oxide is a component in special kinds of steel that is used for automobile parts, springs, and ball bearings. Most of the vanadium used in the United States is used to make steel 38). Vanadium oxide is a yellow-orange powder, dark-gray flakes, or yellow crystals. Vanadium is also mixed with iron to make important parts for aircraft engines. Small amounts of vanadium are used in making rubber, plastics, ceramics, and other chemicals.
What is vanadium used for?
As an important raw material, vanadium is extensively used in modern industry to produce steel and to manufacture automobiles, shipyards, fertilizers, etc. 39). Vanadium is used in many industries and applications, from automobiles, power generation, and hand tools, to ships, industrial tools and aeroplanes 40).
- Aerospace: Vanadium is found in aircraft components including landing gear using ultra high strength steel 300M, and airframe and engine parts using titanium alloys such as Ti-6Al-4V.
- Oil and Gas Pipelines: High strength, tough and weldable HSLA plate and coil steels containing vanadium are widely used for oil and gas transmission pipelines.
- Power Stations: Power stations rely on vanadium in many high strength creep resistant components using carbon and stainless steels subjected to high temperatures and corrosive environments.
- Rails: Vanadium can be added to improve the properties of high performance pearlitic and bainitic rail steels required for extreme service conditions.
- Ships: In ship plate and bulb flats vanadium is used to achieve high strength and toughness, while maintaining excellent weldability.
- Anti-Seismic Rebars: Vanadium microalloyed high strength rebar is a safe, reliable and cost effective solution for reinforced concrete construction in earthquake prone regions.
- Automotive: Many applications of vanadium exist in modern automobiles including HSLA and AHSS for body structure, and microalloyed forging steels for engine and chassis.
- Bridges: Steel bridges often use vanadium microalloyed HSLA steel due the excellent combination of high strength, toughness and weldability.
- Construction: Vanadium plays an essential role in providing high strength and cost effective solutions for the construction sector.
- Fusion Reactors: Vanadium alloys are being investigated as potential candidate materials for fusion reactors.
- Wind Turbines: Wind turbine towers benefit from lighter weight and weldability when vanadium microalloyed HSLA steel plate is used.
- Transmission Towers: Electricity transmission towers are lighter and higher performance due to high strength, tough and weldable vanadium microalloyed HSLA section steels.
- Hand Tools: Vanadium and chromium are added to increase the surface hardness and resistance to distortion under load in many hand tools.
- High Strength Bolts: Vanadium is often added to high strength bolts to improve their resistance to hydrogen induced delayed failure.
- Knives: Many steels used for high quality knives contain vanadium to increase hardness and edge retention.
- Tools & Dies: Tools and dies, used to manufacture engineering components and everyday articles, often contain vanadium for improved cutting edge hardness and wear resistance.
- Machinery/Bearings: In high strength heat treated steels used in machinery vanadium is often an important component improving strength and toughness due to temper resistance.
- Vanadium Redox Flow Battery: The Vanadium Redox Flow Battery uses vanadium electrolyte to store energy and enable wider use of renewable power generation such as wind and solar.
China is the world’s biggest vanadium-producing country, and it has the fastest growing and highest consumption of vanadium products in the world 41). Vanadium pollution is becoming an important environmental concern in China. General population exposure to vanadium is mainly via consuming food and drinking water. Contaminated air from the combustion of petroleum fuels is also a potential source of vanadium exposure 42).
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