Reducing occupational lead exposures: Strengthened standards for a healthy workforce

Assessment of occupational exposure to lead among workers engaged in a city bus garage in Addis Ababa, Ethiopia: a comparative cross-sectional study

BACKGROUND

Lead is one of the most nonessential toxic heavy metal agents found in automotive garages. The occupational exposure of garage workers to lead commonly poses acute and chronic health risks that can be prevented. In Ethiopia, there have been limited studies on lead exposure among garage workers, who overemphasize exposure to lead. This study aimed to assess occupational blood lead levels and associated factors in garage workers using a cross-sectional comparative design.

METHODS

A comparative cross-sectional study design was used to compare the occupational blood lead levels of 36 randomly selected garage workers and 34 office workers who were matched by age and sex. Blood specimens were collected by trained medical laboratory experts. The collected blood samples were tested in a certified laboratory using a microwave plasma atomic emission spectrometry (MP-AES) device at a wavelength of 405.78 nm. Excel and SPSS Version 26 were used for data management and analysis, respectively.

RESULTS

The mean (SD) age of the exposed group was 39.0 (7.5) years, whereas the mean age of the unexposed group was 38.0 (6.1) years. The occupational mean (SD) blood-lead-level in the exposed groups was 29.7 (12.2) µg/dl, compared to 14.8 (9.9) µg/dl among the unexposed groups. The mean blood-lead level among the exposed workers was significantly different from that among the unexposed workers (P < 0.01). Of all the study participants, only 22.2% of the exposed groups had blood lead levels higher than the World Health Organization's recommended limit of 40 µg/dl. The main significant predictors of occupational blood-lead-level exposure among workers were extra working hours, service years, and having a previous (prior) employment history in a garage. The occupations of the two groups did not significantly differ in terms of blood-lead levels (p > 0.05).

CONCLUSIONS

The BLL of the Garage workers was significantly greater than that of the Non-Garage workers. Hence, it is advised that garage management should encourage workers to use exposure prevention methods, such as washing their hands before eating and taking showers after the completion of work, by providing regular occupational safety training.

Automated lead toxicity prediction using computational modelling framework

Background

Lead, an environmental toxicant, accounts for 0.6% of the global burden of disease, with the highest burden in developing countries. Lead poisoning is very much preventable with adequate and timely action. Therefore, it is important to identify factors that contribute to maternal BLL and minimise them to reduce the transfer to the foetus. Literacy and awareness related to its impact are low and the clinical establishment for biological monitoring of blood lead level (BLL) is low, costly, and time-consuming. A significant contribution to an infant's BLL load is caused by maternal lead transfer during pregnancy. This acts as the first pathway to the infant's lead exposure. The social and demographic information that includes lifestyle and environmental factors are key to maternal lead exposure.

Results

We propose a novel approach to build a computational model framework that can predict lead toxicity levels in maternal blood using a set of sociodemographic features. To illustrate our proposed approach, maternal data comprising socio-demographic features and blood samples from the pregnant woman is collected, analysed, and modelled. The computational model is built that learns from the maternal data and then predicts lead level in a pregnant woman using a set of questionnaires that relate to the maternal's social and demographic information as the first point of testing. The range of features identified in the built models can estimate the underlying function and provide an understanding of the toxicity level. Following feature selection methods, the 12-feature set obtained from the Boruta algorithm gave better prediction results (kNN = 76.84%, DT = 74.70%, and NN = 73.99%).

Conclusion

The built prediction model can be beneficial in improving the point of care and hence reducing the cost and the risk involved. It is envisaged that in future, the proposed methodology will become a part of a screening process to assist healthcare experts at the point of evaluating the lead toxicity level in pregnant women. Women screened positive could be given a range of facilities including preliminary counselling to being referred to the health centre for further diagnosis. Steps could be taken to reduce maternal lead exposure; hence, it could also be possible to mitigate the infant's lead exposure by reducing transfer from the pregnant woman.

Evaluation and updates to the Leggett model for pharmacokinetic modeling of exposure to lead in the workplace - Part II adjustments to the adult exposure model, confirmation of Leggett+, and modeling of workplace exposure

California's Office of Environmental Health Hazard Assessment has updated the comprehensive age-specific model of lead metabolism in humans published by Richard W. Leggett in 1993. The updated model, called Leggett+, was introduced in a peer-reviewed report in 2013. The Leggett + model simulates the relationship between blood lead and exposure in the workplace. Leggett + includes a workplace exposure model comprising respiratory tract intake (workplace lead inhaled by a worker) and uptake (lead absorbed into the blood from the respiratory tract plus uptake from ambient air and diet). The latter is calculated as intake times an inhalation transfer coefficient plus background uptake. An adjusted adult systemic model describes the metabolism of the absorbed lead. This paper provides details about the workplace exposure and uptake elements of Leggett+, an updated approach to calibrating an inhalation transfer coefficient, confirmation of the model's performance in predicting blood lead levels from workplace studies, and predictions of blood lead levels from simulated exposures to workplace airborne lead over a working lifetime. Blood lead relative to airborne lead concentrations in a standard workplace scenario predicted by Leggett + was similar to corresponding relationships from four published workplace studies. Leggett + predictions displayed a good fit to regression equations when other key factors were considered such as pre-employment blood lead and ongoing background intake of lead, workplace air concentration, lead aerosol characteristics, and worker activity levels. The comprehensive Leggett + model can simulate plausible workplace air-blood lead relationships from a broad range of worker exposures. The inhalation transfer coefficient of 0.30, derived from empirical data described in the 2013 report has been reexamined. The original estimate continues to represent a plausible mid-point for a coefficient derived from an expanded range of theoretical particle size distributions deposited in the upper and lower regions of the respiratory tract considering intake during sedentary and outdoor activity breathing scenarios. This coefficient is slightly lower than the value of 0.35 estimated for unknown forms of lead by Leggett in 1993.

Potential Health Risks of Lead Exposure from Early Life through Later Life: Implications for Public Health Education

Lead (Pb) exposure has been a serious environmental and public health problem throughout the world over the years. The major sources of lead in the past were paint and gasoline before they were phased out due to its toxicity. Meanwhile, people continue to be exposed to lead from time to time through many other sources such as water, food, soil and air. Lead exposure from these sources could have detrimental effects on human health, especially in children. UNICEF reported that approximately 800 million children have blood lead levels (BLLs) at or above 5 micrograms per deciliter (µg/dL) globally. This paper reports on the potential risks of lead exposure from early life through later life. The articles used in this study were searched from databases such as Springer, Science Direct, Hindawi, MDPI, Google Scholar, PubMed and other academic databases. The levels of lead exposure in low income and middle-income countries (LMICs) and high-income countries (HICs) were reported, with the former being more affected. The intake of certain nutrients could play an essential role in reducing (e.g., calcium and iron) or increasing (e.g., high fat foods) lead absorption in children. Elevated blood lead levels may disturb the cells' biological metabolism by replacing beneficial ions in the body such as calcium, magnesium, iron and sodium. Once these ions are replaced by lead, they can lead to brain disorders, resulting in reduced IQ, learning difficulties, reduced attention span and some behavioral problems. Exposure to lead at an early age may lead to the development of more critical problems later in life. This is because exposure to this metal can be harmful even at low exposure levels and may have a lasting and irreversible effect on humans. Precautionary measures should be put in place to prevent future exposure. These will go a long way in safeguarding the health of everyone, most especially the young ones.

Lead exposure and antisocial behavior: A systematic review protocol

BACKGROUND

Lead exposure remains highly prevalent worldwide despite decades of research highlighting its link to numerous adverse health outcomes. In addition to well-documented effects on cognition, there is growing evidence of an association with antisocial behavior, including aggression, conduct problems, and crime. An updated systematic review on this topic, incorporating study evaluation and a developmental perspective on the outcome, can advance the state of the science on lead and inform global policy interventions to reduce exposure.

OBJECTIVES

We aim to evaluate the link between lead exposure and antisocial behavior. This association will be investigated via a systematic review of human epidemiological and experimental nonhuman mammalian studies.

METHODS

The systematic review protocol presented in this publication is informed by recommendations for the conduct of systematic reviews in toxicology and environmental health research (COSTER) and follows the study evaluation approach put forth by the U.S. EPA Integrated Risk Information System (IRIS) program.

DATA SOURCES

We will search the following electronic databases for relevant literature: PubMed, BIOSIS and Web of Science. Search results will be stored in EPA's Health and Environmental Research Online (HERO) database.

STUDY ELIGIBILITY AND CRITERIA

Eligible human epidemiological studies will include those evaluating any population exposed to lead at any lifestage via ingestion or inhalation exposure and considering an outcome of antisocial behavior based on any of the following criteria: psychiatric diagnoses (e.g., oppositional defiant disorder (ODD), conduct disorder (CD), disruptive behavior disorders (DBD)); violation of social norms (e.g., delinquency, criminality); and aggression. Eligible experimental animal studies will include those evaluating nonhuman mammalian studies exposed to lead via ingestion, inhalation, or injection exposure during any lifestage. The following outcomes will be considered relevant: aggression; antisocial behavior; and altered fear, anxiety, and stress response.

STUDY APPRAISAL AND SYNTHESIS METHODS

Screening will be conducted with assistance from an artificial intelligence application. Two independent reviewers for each data stream (human, animal) will screen studies with highest predicted relevance against pre-specified inclusion criteria at the title/abstract and full-text level. Study evaluation will be conducted using methods adapted from the U.S. EPA IRIS program. After data extraction, we will conduct a narrative review and quantitative meta-analysis on the human epidemiological studies as well as a narrative review of the experimental animal studies. We will evaluate the strength of each evidence stream separately and then will develop a summary evidence integration statement based on inference across evidence streams.

Industries With the Highest Occupational Blood Lead Test Results, California Occupational Blood Lead Registry, 2020‒2021

Objectives. To evaluate the focused surveillance of blood lead results of 20 micrograms per deciliter (µg/dL) of venous blood and higher received by the California Occupational Blood Lead Registry (Registry) because of new legislation concerning occupational lead poisoning. Methods. We used occupational blood lead results reported to the Registry from January 1, 2020, to December 31, 2021, to describe the current industries with workers having the highest levels of lead poisoning. Results. The Registry received 239 blood lead levels (BLLs) of 20 µg/dL or higher for 151 adults with occupational lead exposure in 28 industries over the study period. Worker BLLs ranged from 20 µg/dL to 55 µg/dL. The industries with the greatest number of workers were storage battery manufacturing, painting contractors, and shooting ranges. Conclusions. Occupational lead poisoning is a health concern across numerous industries in California. The current outdated state and federal occupational lead standards would not require removal from lead work for any of the workers in this study despite extensive evidence of harm at lower BLLs. Strengthened standards could support public health initiatives for worker protection and reduce take-home lead to family members. (Am J Public Health. 2022;112(S7):S690-S694. https://doi.org/10.2105/AJPH.2022.307002).

Lead Industry Influence in the 21st Century: An Old Playbook for a "Modern Metal"

In recent years, lead poisoning has received increasing attention as lead production continues to grow and the industry shifts the most polluting processes (e.g., smelting ore and recycling batteries) to low- and middle-income countries. The hazards associated with lead exposures have been well known for centuries while the industry actively promoted lead products. Less well known is how the industry continues to promote the "safe and responsible" use of lead and support research to question the underlying science and avoid regulation. Here I explore the historical context for recent actions that the industry has taken to ensure its longevity. Lead industry associations continue to employ some of the same themes that have proven successful in the past. Efforts to forestall regulatory initiatives to reduce emissions and restrict lead applications continue. Large battery manufacturers and recyclers and their associations place blame on informal-sector recycling to draw focus away from their own emissions. They have sought the cooperation of hired scientific experts and have funded United Nations organizations and nongovernmental organizations to deflect attention from their own contributions to global lead poisoning. (Am J Public Health. 2022;112(S7):S723-S729. https://doi.org/10.2105/AJPH.2022.306960).

Comparative efficacy of silibinin and nano-silibinin on lead poisoning in Male Wistar rats

Lead (Pb) is an environmental neurotoxin that can lead to toxicity. It has shown that tissues can be exposed to oxidative stress in lead poisoning. Since silymarin is a natural agent with antioxidant effects, this study aimed to investigate the antioxidant and chelation effects of silibinin and nano-silibinin on the oxidative stress status in lead-poisoned rats. Sixty male Wistar rats randomly divided into ten groups (n = 6). Control and Pb groups treated with or without silibinin and nano-silibinin for six days. Following measuring of weight and blood lead levels, biochemical antioxidant parameters evaluated. Finally, a histopathological examination of the liver performed. In this experiment, silibinin and more efficiently nano-silibinin prevented weight loss and blood lead level elevation induced by lead. Also, they increased the attenuated levels of superoxide dismutase (SOD) activity, catalase (CAT), total thiol molecules (TTM), glutathione (GSH), and total antioxidant capacity (TAC). Lead-induced elevation of lipid peroxidation products (MDA) and nitric oxide (NO) normalized to the standard level in silibinin and especially nano-silibinin groups. These data suggested that silibinin and especially nano-silibinin can decrease blood lead levels and prevent weight loss and oxidative stress in the lead-poisoned rat's model.

Workers should take steps to mitigate surface lead exposure when using lead-containing personal protective equipment

Veterinary workers use lead shielding for protection against harm from ionizing radiation during diagnostic imaging. Surface lead on shielding has been reported as a potential exposure hazard. The purpose of this prospective, analytical, descriptive study was to measure surface lead on lead-containing shielding in the field service and small animal radiology areas of a veterinary teaching hospital, and to examine potential risk factors for surface lead. Surface lead on a convenience sample of 54 lead shielding items was measured in a commercial laboratory using inductively coupled plasma mass spectrometry. The median and range of surface lead for aprons, thyroid collars, and gloves were 3.6 μg/dm² (range, 1.3-22.4 μg/dm² ), 23.1 μg/dm² (range, 2.6-116 μg/dm² ), and 134 μg/dm² (range, 1.5-155 μg/dm² ), respectively. In the final multivariable analysis, the mean surface lead on thyroid collars and gloves was higher than on aprons (relative differences 4.8, 95% confidence interval [CI] 2.2, 10.5, P < 0.001; and 9.5, 95% CI 4.4, 20.6, P < 0.001, respectively). The mean surface lead on shielding in the worst condition was higher than on shielding in the intermediate and best conditions (P < 0.001). Lead shielding provides effective protection against the harmful effects of ionizing radiation, and shielding should always be worn during radiation exposure. Based on our findings and the common use of lead shielding in veterinary workplaces, we recommend that employers inform workers of this hazard and provide training on steps to mitigate exposure, including the use of disposable gloves when wearing lead shielding and handwashing after use.

Assessment of lead exposure controls on bridge painting projects using worker blood lead levels

A retrospective analysis of worker blood lead levels (BLL) was conducted using blood lead data collected by four bridge painting contractors before and after lead exposure. The objective of the study was to evaluate the effectiveness of exposure controls in preventing elevated blood lead levels (>25 μg/dl) during bridge painting projects. The contractors selected for the study submitted BLL data for 289 workers representing ten work tasks and 11 bridge painting projects. In total, 713 blood lead levels results were evaluated. The mean blood lead level for all work classifications combined was 10.9 μg/dl at baseline compared with 14.9 μg/dl after two months of exposure and 15.0 μg/dl after four months of exposure. Two months after initial exposure, 29% of the painters and 35% of the laborers had a 10 μg/dl incremental increase or greater in blood lead level. Likewise, 18% of the painters and 26% of the laborers had a blood lead level greater than 25 μg/dl during the same time. The blood lead levels that exceeded the 25 μg/dL threshold ranged from 30μg/dL-63 μg/dL for painters and 26 μg-56 μg/dL for laborers. All work tasks with high-intensity exposure (abrasive blaster/painter, abrasive blaster, painter & laborer) experienced an average blood lead level increase that ranged from 0.2 μg/dl to 8.9 μg/dl two months after initial exposure. Blood lead testing conducted after modified exposure controls (two months after the initial follow-up blood testing) were implemented showed a decrease in average blood lead levels (range -0.14 μg/dl to -2.7 μg/dl) for two high-intensity exposure work tasks. In comparison, the other two high-intensity work tasks had moderate increases (range 1 μg/dl to 2.4 μg/dl). The modified exposure controls included an increase in the air velocity inside of the work containment and an administrative control in the form of additional worker training on lead exposure prevention. The reduction in the 95th percentile (point estimate) BLL exposure profile for each exposure group at the 4-month follow-up blood testing period is associated with modified exposure controls. Ineffective exposure controls were identified through the analysis of worker BLLs. We found two exposure groups (laborer and painter) whose 95th percentile (point estimate) exposure profile was greater than the OSHA construction lead standard's targeted BLL goal (25 μg/dl) during the first two months of exposure. Our research findings provide support for monthly blood lead testing after baseline until blood lead levels are controlled to an acceptable concentration.

Evaluation and updates to the Leggett model for pharmacokinetic modeling of exposure to lead in the workplace - Part I adjustments to the adult systemic model

California's Division of Occupational Safety and Health has initiated a process to update its standards for exposure to lead in workplaces. In support of this effort, the state's Office of Environmental Health Hazard Assessment evaluated the age-specific, bio-kinetic model of lead metabolism in humans, originally published by R.W. Leggett in 1993. This model was ultimately chosen for its physiologic realism and practicality in characterizing the relationship between air lead concentrations and blood lead levels in chronically exposed worker and its practicality in making necessary adjustments. Leggett's original model systematically under-predicts bone and blood levels in workers such that several adjustments to the parameters are needed to improve predictions for occupational exposure scenarios. The aim of this work is to incorporate new information about the bio-kinetics of lead in workers and to adjust the Leggett model to improve its predictions.The Leggett model was evaluated by comparing its predictions with information on lead concentrations in bone, blood, and urine from workers and other chronically exposed adults. Key model parameters were identified based upon a review of the relevant exposure assessment and modeling literature. Adjustments to the model parameters were made based on empirical evidence. They included reducing the level of lead in blood (BLL) where the rate of decrease in red blood cell binding begins and ends, lead accumulation rate in cortical bone, the rate of lead elimination in trabecular bone, and rate of lead transferred from diffusible plasma to urine. Regression methods and visual inspection of plotted data were used to assess the effect of adjustments on model predictions. When compared with the original, the adjusted Leggett model more accurately predicted lead concentrations observed in active and retired workers. Also, the adjusted Leggett model required less lead uptake to reach the same BLLs for BLLs less than 25 µg/dL and more time for BLLs to decline than the original Leggett model. These findings are important for defining an adequately protective occupational standard for lead exposure.

Eliminating Take-Home Exposures: Recognizing the Role of Occupational Health and Safety in Broader Community Health

Toxic contaminants inadvertently brought from the workplace to the home, known as take-home or paraoccupational exposures, have often been framed as a problem that arises due to unsanitary worker behavior. This review article conceptualizes take-home exposures as a public health hazard by (i) investigating the history of take-home contaminants and how they have been studied, (ii) arguing that an ecosocial view of the problem is essential for effective prevention, (iii) summarizing key structural vulnerabilities that lead populations to be at risk, and (iv) discussing future research and prevention effort needs. This article reframes take-home exposures as one of many chronic pathways that contributes to persistent health disparities among workers, their families, and communities. Including the role of work in community health will increase the comprehensiveness of prevention efforts for contaminants such as lead and pesticides that contribute to environmental disparities.

Ameliorative effect of curcumin on lead-induced hematological and hepatorenal toxicity in a rat model

INTRODUCTION

Lead (Pb) is a ubiquitous toxic heavy metal that inflicts numerous clinical consequences on humans. Curcumin is the principal component of turmeric, which is reported to have antioxidative properties. This study aimed at evaluating the ameliorative effects of curcumin on Pb-induced hepatorenal toxicity in a rat model.

METHODS

Thirty-six male Sprague-Dawley rats were randomly assigned into five groups with 12 rats in the control (normal saline) and six rats each for the lead-treated group (LTG) (50 mg/kg lead acetate [Pb acetate] for 4 weeks), recovery group (50 mg/kg Pb acetate for 4 weeks and left with no treatment for another 4 weeks), treatment group 1 (Cur100) (50 mg/kg Pb acetate for 4 weeks, followed by 100 mg/kg curcumin for 4 weeks), and treatment group 2 (Cur200) (50 mg/kg Pb acetate for 4 weeks, followed by 200 mg/kg curcumin for 4 weeks). All the experimental groups received oral treatments via orogastric-tube on alternate days. Pb concentration in the liver and kidney of the rats were evaluated using inductive-coupled plasma mass spectrometry techniques.

RESULTS

Pb-administered rats revealed significant alteration in oxidative status and increased Pb concentration in their liver and kidney with obvious reduction of hemogram and increased in leukogram as well as aberration in histological architecture of the liver and kidney. However, treatment with curcumin reduces the tissue Pb concentrations and ameliorates the above mention alterations.

CONCLUSIONS

The results in this study suggested that curcumin attenuates Pb-induced hepatorenal toxicity via chelating activity and inhibition of oxidative stress.

Curcumin Attenuates Lead-Induced Cerebellar Toxicity in Rats via Chelating Activity and Inhibition of Oxidative Stress

Lead (Pb) is a toxic, environmental heavy metal that induces serious clinical defects in all organs, with the nervous system being its primary target. Curcumin is the main active constituent of turmeric rhizome (Curcuma longa) with strong antioxidant and anti-inflammatory properties. This study is aimed at evaluating the therapeutic potentials of curcumin on Pb-induced neurotoxicity. Thirty-six male Sprague Dawley rats were randomly assigned into five groups with 12 rats in the control (normal saline) and 6 rats in each of groups, i.e., the lead-treated group (LTG) (50 mg/kg lead acetate for four weeks), recovery group (RC) (50 mg/kg lead acetate for four weeks), treatment group 1 (Cur100) (50 mg/kg lead acetate for four weeks, followed by 100 mg/kg curcumin for four weeks) and treatment group 2 (Cur200) (50 mg/kg lead acetate for four weeks, followed by 200 mg/kg curcumin for four weeks). All experimental groups received oral treatment via orogastric tube on alternate days. Motor function was assessed using a horizontal bar method. The cerebellar concentration of Pb was evaluated using ICP-MS technique. Pb-administered rats showed a significant decrease in motor scores and Superoxide Dismutase (SOD) activity with increased Malondialdehyde (MDA) levels. In addition, a marked increase in cerebellar Pb concentration and alterations in the histological architecture of the cerebellar cortex layers were recorded. However, treatment with curcumin improved the motor score, reduced Pb concentration in the cerebellum, and ameliorated the markers of oxidative stress, as well as restored the histological architecture of the cerebellum. The results of this study suggest that curcumin attenuates Pb-induced neurotoxicity via inhibition of oxidative stress and chelating activity.