Aaron J. Specht

Portable XRF Technology to Quantify Pb in Bone In Vivo

Lead is a ubiquitous toxicant. Bone lead has been established as an important biomarker for cumulative lead exposures and has been correlated with adverse health effects on many systems in the body. K-shell X-ray fluorescence (KXRF) is the standard method for measuring bone lead, but this approach has many difficulties that have limited the widespread use of this exposure assessment method. With recent advancements in X-ray fluorescence (XRF) technology, we have developed a portable system that can quantify lead in bone in vivo within 3 minutes. Our study investigated improvements to the system, four calibration methods, and system validation for in vivo measurements. Our main results show that the detection limit of the system is 2.9 ppm with 2 mm soft tissue thickness, the best calibration method for in vivo measurement is background subtraction, and there is strong correlation between KXRF and portable LXRF bone lead results. Our results indicate that the technology is ready to be used in large human population studies to investigate adverse health effects of lead exposure. The portability of the system and fast measurement time should allow for this technology to greatly advance the research on lead exposure and public/environmental health.

XRF-measured bone lead (Pb) as a biomarker for Pb exposure and toxicity among children diagnosed with Pb poisoning

Abstract Childhood lead (Pb) poisoning remains a global issue, especially in industrial areas. In this study, 115 children with average age 5.7 years were recruited as either patient diagnosed with Pb poisoning or controls at Xinhua Hospital in China. The subjects’ bone Pb was measured with a K-shell X-ray fluorescence (KXRF) and a portable X-ray fluorescence (XRF) system. A significant correlation between KXRF bone Pb and blood Pb and portable XRF and KXRF measurements were observed. The half-life of blood-lead was calculated to be 9.96 ± 3.92 d. Our results indicate that bone is a useful biomarker for Pb in children.

Feasibility of a portable X-ray fluorescence device for bone lead measurements of condor bones

Lead based ammunition is a primary source of lead exposure, especially for scavenging wildlife. Lead poisoning remains the leading cause of diagnosed death for the critically endangered California condors, which are annually monitored via blood tests for lead exposure. The results of these tests are helpful in determining recent exposure in condors and in defining the potential for exposure to other species including humans. Since condors are victim to acute and chronic lead exposure, being able to measure both would lend valuable information on the rates of exposure and accumulation through time. A commercial portable X-ray fluorescence (XRF) device has been optimized to measure bone lead in vivo in humans, but this device could also be valuable for field measurements of bone lead in avian species. In this study, we performed measurements of bone Pb in excised, bare condor bones using inductively coupled plasma mass spectrometry (ICP-MS), a cadmium 109 (Cd-109) K-shell X-ray fluorescence (KXRF) system, and a portable XRF system. Both KXRF and portable XRF bone Pb measurement techniques demonstrated good correlations with ICP-MS results (r=0.93 and r=0.92 respectively), even with increasing skin thickness (r=0.86 between ICP-MS and portable XRF at 1.54mm of soft tissue). In conclusion, our results suggest that a portable XRF could be a useful option for measurement of bone Pb in avian species in the field.

Potential Sex Differences Relative to Autism Spectrum Disorder and Metals

Purpose of reviewThis study aims to summarize the current body of literature on the relationship between various toxic metals exposures (i.e., aluminum, antimony, arsenic, beryllium, cadmium, chromium, lead, manganese, and nickel) and autism spectrum disorder (ASD), with a focus on potential sex differences in these associations.Recent findingsSex differences in ASD diagnosis and mutagenic effects of toxic exposures indicate that sex differences may play a major part in the causal relationship of any potential associations seen; however, we were only able to find three studies that reported on sex differences in observed associations with toxic metals exposure and ASD. We also found several studies investigating associations between ASD and metals exposures, including 11 on aluminum, 6 on antimony, 15 on arsenic, 5 on beryllium, 17 on cadmium, 11 on chromium, 25 on lead, 14 on manganese, and 13 on nickel with markers of exposure in hair, urine, blood, teeth, fingernails, and air pollution. Results for each metal were conflicting, but studies on cadmium and lead yielded the highest proportion of studies with positive results (72% and 36%, respectively).SummaryBased on our examination of existing literature, the current evidence warrants a considerable need for evaluations of sex differences in future studies assessing the association between metals exposures and ASD. Additionally, failure to account for potential sex differences could result in bias and misinterpretation of exposure-disease relationships.

Measurements of Strontium Levels in Human Bone In Vivo Using Portable X-ray Fluorescence (XRF)

Measurement of bone strontium (Sr) is vital to determining the effectiveness of Sr supplementation, which is commonly used for the treatment of osteoporosis. Previous technology uses radioisotope sources and bulky equipment to measure bone Sr. This study demonstrates the effectiveness of portable X-ray fluorescence (XRF) for bone Sr measurement and validates it using data from a population of 238 children. We identified correlations between bone Sr and age in our participants.

Quantification of manganese and mercury in toenail in vivo using portable x-ray fluorescence (XRF)

Abstract Background and objective: Toenail is an advantageous biomarker to assess exposure to metals such as manganese and mercury. Toenail Mn and Hg are in general analyzed by chemical methods such as inductively coupled plasma mass spectrometry and atomic absorption spectrophotometry. In this project, a practical and convenient technology—portable X-ray florescence (XRF)—is studied for the noninvasive in vivo quantification of manganese and mercury in toenail. Material and methods: The portable XRF method has advantages in that it does not require toenail clipping and it can be done in 3 min, which will greatly benefit human studies involving the assessment of manganese and mercury exposures. This study mainly focused on the methodology development and validation which includes spectral analysis, system calibration, the effect of toenail thickness, and the detection limit of the system. Manganese- and mercury-doped toenail phantoms were made. Calibration lines were established for these measurements. Results: The results show that the detection limit for manganese is 3.65 μg/g (ppm) and for mercury is 0.55 μg/g (ppm) using 1 mm thick nail phantoms with 10 mm soft tissue underneath. Discussion and conclusion: We conclude that portable XRF is a valuable and sensitive technology to quantify toenail manganese and mercury in vivo.

Lead exposure biomarkers in the Common Loon

Lead in fishing tackle is a significant source of exposure to the environment, wildlife, and potentially humans. Common Loons (Gavia immer) are exposed to lead by eating fish which have lead tackle, or ingesting fishing weights or spent ammunition when they ingest small stones to aid in digestion. Blood lead is traditionally used as a biomarker of exposure in loons, but it only reflects recent exposures. Cumulative exposure measured via bone lead may better reflect the overall health of loons and their aquatic habitat. This study compared a portable x-ray fluorescence (XRF) device for measurement of bone lead with and without tissue overlying the bone on loon cadavers with measurements made by inductively coupled plasma mass spectrometry (ICP-MS) of different tissues from the loons. For this study we had 75 bone samples, 19 body fluid samples, and 17 liver lead samples. We found significant correlations between portable XRF bone lead measurements made with overlying tissue and ICP-MS measures of bone lead (R = 0.88), body fluid lead (R = 0.65), and liver lead (R = 0.71). Bone lead was found to be higher in loons collected from non-coastal regions. In assessing lead-related cause of death, bone lead proved more predictive than liver lead. Future studies should investigate the value of these biomarkers for both aquatic health and loon health to further validate our findings.

Bone lead levels in an environmentally exposed elderly population in shanghai, China

This study looked at measurements of lead (Pb) in a pilot population of environmentally exposed elderly residents of Shanghai, China and presented the first set of bone Pb data on an elderly Chinese population. We found that with environmental exposures in this population using K-shell x-ray fluorescence (KXRF) bone Pb measurements 40% of the individuals had bone Pb levels above the nominal detection limit with an average bone lead level of 4.9 ± 3.6 μg/g. This bone lead level is lower than comparable values from previous studies of community dwelling adults in US cities. This population had a slightly higher geometric mean blood Pb of 2.6 μg/dL than the adult US population. The main conclusion of this data is that in Shanghai there is environmental exposure to Pb, measured through blood and bone, which should be further investigated to assess the health impact of this exposure.

Study of occupation and amyotrophic lateral sclerosis in a Danish cohort

Objectives Several manuscripts have proposed associations between amyotrophic lateral sclerosis (ALS) and occupational toxicant exposures—not to mention physical activity and trauma/injury. Some have also reported associations in investigations of specific occupations. Using data from a prospective Danish cohort study, we investigated the association between employment in certain industries and ALS diagnosis. Methods We identified 1826 ALS cases who were 25 years old or less in 1964 and diagnosed from 1982 to 2013 from the Danish National Patient Registry then matched 100 population controls to each case based on birth year and sex. Demographic data were linked to the Danish Pension Fund to determine occupation history. Conditional logistic regression models were adjusted for socioeconomic status, marital status and residential location at the index date. Results There was an increase in odds of ALS among men who worked in agriculture, hunting, forestry or fishing (adjusted OR (aOR)=1.21; 95% CI 1.02 to 1.45). There was also a positive association for men employed in construction (aOR=1.21; 95% CI 1.05 to 1.39). In women, a protective association was seen with employment in the cleaning industry (aOR=0.69; 95% CI 0.52 to 0.93). Conclusions Our study shows various occupations with exposure to toxicants, such as diesel exhaust and lead, and strenuous physical activity associated with increased odds of ALS in men. Future studies should have a particular focus on gathering detailed information on physical exertion and toxicant exposures specific to certain job tasks.

Childhood lead biokinetics and associations with age among a group of lead-poisoned children in China

Childhood lead exposure has been shown to have a significant effect on neurodevelopment. Many of the biokinetics involved with lead biomarkers in children still remain unknown. Two hundred fifty (157 in the exposed group and 93 controls) children were enrolled in our study and lead exposed children returned for multiple visits for measurement of blood and bone lead and chelation treatment. We demonstrated that the correlation between blood and bone lead increased with subsequent visits. We calculated the blood lead half-life for 50 patients, and found a significant (p-value < 0.001) positive correlation with age. For ages 1–3 years (N = 17), the blood lead half-life was found to be 6.9 ± 4.0 days and for 3+ years it was found to be (N = 33) 19.3 ± 14.1 days. In conclusion, the turnover of lead in children is faster than in adults. Our results indicate that blood lead is a more acute biomarker of exposure than previously thought, which will impact studies of children’s health using blood lead as a biomarker.