The effect of lead on male fertility: a time to pregnancy (TTP) study

Enhanced removal of toxic Cr(vi) and Pb(ii) from water using carboxylic terminated Ti3C2Tx nanosheets

The discharge of Cr(vi)and Pb(ii) contaminants into water resources through industrial waste induces a considerable risk to human and marine life, which demands an effective removal of these toxic metal ions (MI) from the aquatic environment. This study presents a remarkable adsorption performance of the carboxylic terminated Ti3C2Tx nanosheets synthesized using ammonium bifluoride and citric acid and applied as adsorbents for the removal of Cr(vi)and Pb(ii) from water. Adsorption efficiency was evaluated under sonication, MI concentration, and solution temperature at pH 5.5. Maximum adsorption capacities of 1090 mg g-1 and 1135 mg g-1 for Cr(vi) and Pb(ii) were attained within 7 and 4 minutes, respectively. Moreover, adsorption kinetic and isotherm studies were conducted, and the experimental data was found to fit well with pseudo-second-order reaction and Freundlich models. It was also established that the main interactions to drive the adsorption reactions were the electrostatic forces between the adsorbates and Ti3C2Tx adsorbent. Furthermore, (-COOH) and (-OH) terminal groups were the main contributors to the adsorption of Cr(vi) and Pb(ii) pollutants through an ion exchange mechanism. Besides the ion exchange mechanism, chemical coordination, entrapment of the adsorbates, and van der Waals forces lead to a physiochemical interaction between the MI and Ti3C2Tx nanosheets. In addition, Ti3C2Tx nanosheets showed better selectivity towards Pb(ii) removal than Cr(vi) in an aqueous solution. The nanosheets also exhibited more than 80% removal efficiency even after six cycles of regeneration and reusability. Additionally, Ti3C2Tx nanosheets offered superior adsorption performance for Cr(vi) and Pb(ii) compared to previously reported titanium carbide MXenes and activated carbon-based adsorbents. Hence, these high-quality and efficient Ti3C2Tx nanosheets can potentially eradicate other hazardous MI contaminants from wastewater.

Trace elements in Foodstuffs from the Mediterranean Basin-Occurrence, Risk Assessment, Regulations, and Prevention strategies: A review

Trace elements (TEs) are chemical compounds that naturally occur in the earth's crust and in living organisms at low concentrations. Anthropogenic activities can significantly increase the level of TEs in the environment and finally enter the food chain. Toxic TEs like cadmium, lead, arsenic, and mercury have no positive role in a biological system and can cause harmful effects on human health. Ingestion of contaminated food is a typical route of TEs intake by humans. Recent data about the occurrence of TEs in food available in the Mediterranean countries are considered in this review. Analytical methods are also discussed. Furthermore, a discussion of existing international agency regulations will be given. The risk associated with the dietary intake of TEs was estimated by considering consumer exposure and threshold values such as Benchmark dose lower confidence limit and provisional tolerable weekly intake established by the European Food Safety Authority and the Joint FAO/WHO Expert Committee on Food Additives, respectively. Finally, several remediation approaches to minimize TE contamination in foodstuffs were discussed including chemical, biological, biotechnological, and nanotechnological methods. The results of this study proved the occurrence of TEs contamination at high levels in vegetables and fish from some Mediterranean countries. Lead and cadmium are more abundant in foodstuffs than other toxic trace elements. Geographical variations in TE contamination of food crops clearly appear, with a greater risk in developing countries. There is still a need for the regular monitoring of these toxic element levels in food items to ensure consumer protection.

Turmeric and vitamin C mitigate testicular atrophy induced by lead diacetate via regulation of GRP-78/17β-HSD pathways in rat's model

Occupational and ecological contacts to lead persist as a universal concern. Lead alters most of the physiological processes via enhancing oxidative stress. Thus, this study was purposed to assess the influence of turmeric (TMRC) and/or vitamin C (VIT-C) on Lead diacetate (Lead diAC)-induced testicular atrophy with an emphasis on oxidative stress, inflammation, BAX/STAR and GRP-78/17β-HSD signalling. Rats were injected with Lead diAC and then treated with TMRC and/or VIT-C orally for 1 week. Lead diAC decreased serum testosterone and testicular glutathione levels. It also decreased superoxide dismutase activity. On the contrary, levels of malondialdehyde, tumour necrosis factor-α, IL-1β and caspase-3 were increased. mRNA levels and protein expressions of GRP-78 and BAX were upregulated, while the expression of both steroidogenic acute regulatory protein and 17β-HSD were downregulated. DNA fragmentation was increased as well. These changes were further confirmed by histopathological findings. Supplementation with TMRC and/or VIT-C ameliorated all of the above parameters. In Conclusion: TMRC or VIT-C specially in combination group prevents Lead diAC testicular damage via reduction of oxidative injury as well as inflammation, downregulation of GRP-78/BAX and upregulation of 17β-HSD and STAR expression as well as improvement in the histological architecture of the testis.

Toxic heavy metals: impact on the environment and human health, and treatment with conducting organic polymers, a review

Water pollution by heavy metals has many human origins, such as the burning of fossil fuels, exhaust gases of vehicles, mining, agriculture, and incineration of solid and liquid wastes. Heavy metals also occur naturally, due to volcanoes, thermal springs activity, erosion, infiltration, etc. This water contamination is a threat for living beings because most heavy metals are toxic to humans and to aquatic life. Hence, it is important to find effective techniques for removing these contaminants in order to reduce the level of pollution of the natural waters. In this work, we have reviewed the toxicity of several heavy metals (mercury, lead, cadmium, chromium, nickel), their impact on the environment and human health, and the synthesis and characterization methods of conducting organic polymers (COPs) utilized for the removal of heavy metals from the environment. Therefore, this review was essentially aimed to present recent works and methods (2000-2020) on the environmental impact and toxicity of heavy metals and on the removal of toxic heavy metals, using chemically and/or electrochemically synthesized COPs. We have also stressed the great interest of COPs for the removal of toxic heavy metals from waters.

The Impact of the Flint Water Crisis on Fertility

Flint switched its public water source in April 2014, increasing exposure to lead and other contaminants. We compare the change in the fertility rate and in health at birth in Flint before and after the water switch to the changes in other cities in Michigan. We find that Flint fertility rates decreased by 12 % and that overall health at birth decreased. This effect on health at birth is a function of two countervailing mechanisms: (1) negative selection of less healthy embryos and fetuses not surviving (raising the average health of survivors), and (2) those who survived being scarred (decreasing average health). We untangle this to find a net of selection scarring effect of 5.4 % decrease in birth weight. Because of long-term effects of in utero exposure, these effects are likely lower bounds on the overall effects of this exposure.

Low concentrations of lead decrease the sperm fertilization ability by altering the acrosome reaction in mice

Lead (Pb) exposure at high concentrations is associated with poor sperm quality, acrosome alterations, and low fertilization rate. Sperm capacitation and the acrosome reaction (AR) are required for successful fertilization. Actin polymerization is crucial for correct capacitation, and small GTPases, such as RhoA, Rac1, and Cdc42, are involved. This study aimed to evaluate the effects of Pb on sperm fertilization ability, capacitation, AR, and the mechanisms involved in mice exposed to low Pb concentrations. CD1 mice were exposed to 0.01% Pb²⁺ for 45 days through their drinking water and their spermatozoa were collected from the cauda epididymis-vas deferens to evaluate the following: AR (oAR: initial, sAR: spontaneous, and iAR: induced) using the PNA-FITC assay, sperm capacitation (P-Tyr levels), actin polymerization (phalloidin-TRITC), MDA production (stress oxidative marker), the RhoA, Rac1, and Cdc42 protein levels, and the in vitro fertilization (IVF). After the treatment, the blood Pb (PbB) concentration was 9.4 ± 1.6 μg/dL. Abnormal sperm morphology and the oAR increased (8 and 19%, respectively), whereas the iAR decreased (15%) after a calcium ionophore challenge, and the actin polymerization decreased in the sperm heads (59%) and tails (42%). Rac1 was the only Rho protein to significantly decrease (33%). Spermatozoa from the Pb-treated mice showed a significant reduction in the fertilization rate (19%). Our data suggest that Pb exposure at environmental concentrations (PbB < 10 μg/dL) decreases the acrosome function and affects the sperm fertilization ability; this is probably a consequence of the low Rac1 levels, which did not allow adequate actin polymerization to occur.

Highly efficient heavy-metal extraction from water with carboxylated graphene nanoflakes

Heavy metals such a lead or cadmium have a wide range of detrimental and devastating effects on human health. It is therefore of paramount importance to efficiently remove heavy metals from industrial wastewater streams as well as drinking water. Carbon materials, including graphene and graphene oxide (GO), have recently been advocated as efficient sorption materials for heavy metals. We show that highly carboxylated graphene nanoflakes (cx-GNF) outperform nano-graphene oxide (nGO) as well as traditional GO with respect to extracting Fe²⁺, Cu²⁺, Fe³⁺, Cd²⁺ and Pb²⁺ cations from water. The sorption capacity for Pb²⁺, for example, is more than six times greater for the cx-GNF compared to GO which is attributed to the efficient formation of lead carboxylates as well as strong cation–π interactions. The large numbers of carboxylic acid groups as well as the intact graphenic regions of the cx-GNF are therefore responsible for the strong binding of the heavy metal cations. Remarkably, the performance of the as-made cx-GNF can easily compete with previously reported carbon materials that have undergone additional chemical-functionalisation procedures for the purpose of heavy-metal extraction. Furthermore, the recyclability of the cx-GNF material with respect to Pb²⁺ loading is demonstrated as well as the outstanding performance for Pb²⁺ extraction in the presence of excess Ca²⁺ or Mg²⁺ cations which are often present under environmental conditions. Out of all the graphene materials, the cx-GNF therefore show the greatest potential for future application in heavy-metal extraction processes.

Carboxylated graphene nanoflakes show great potential for heavy-metal extraction from water.

Defining potential roles of Pb(2+) in neurotoxicity from a calciomics approach

Metal ions play crucial roles in numerous biological processes, facilitating biochemical reactions by binding to various proteins. An increasing body of evidence suggests that neurotoxicity associated with exposure to nonessential metals (e.g., Pb(2+)) involves disruption of synaptic activity, and these observed effects are associated with the ability of Pb(2+) to interfere with Zn(2+) and Ca(2+)-dependent functions. However, the molecular mechanism behind Pb(2+) toxicity remains a topic of debate. In this review, we first discuss potential neuronal Ca(2+) binding protein (CaBP) targets for Pb(2+) such as calmodulin (CaM), synaptotagmin, neuronal calcium sensor-1 (NCS-1), N-methyl-d-aspartate receptor (NMDAR) and family C of G-protein coupled receptors (cGPCRs), and their involvement in Ca(2+)-signalling pathways. We then compare metal binding properties between Ca(2+) and Pb(2+) to understand the structural implications of Pb(2+) binding to CaBPs. Statistical and biophysical studies (e.g., NMR and fluorescence spectroscopy) of Pb(2+) binding are discussed to investigate the molecular mechanism behind Pb(2+) toxicity. These studies identify an opportunistic, allosteric binding of Pb(2+) to CaM, which is distinct from ionic displacement. Together, these data suggest three potential modes of Pb(2+) activity related to molecular and/or neural toxicity: (i) Pb(2+) can occupy Ca(2+)-binding sites, inhibiting the activity of the protein by structural modulation, (ii) Pb(2+) can mimic Ca(2+) in the binding sites, falsely activating the protein and perturbing downstream activities, or (iii) Pb(2+) can bind outside of the Ca(2+)-binding sites, resulting in the allosteric modulation of the protein activity. Moreover, the data further suggest that even low concentrations of Pb(2+) can interfere at multiple points within the neuronal Ca(2+) signalling pathways to cause neurotoxicity.

Impaired hypothalamic-pituitary-testicular axis activity, spermatogenesis, and sperm function promote infertility in males with lead poisoning

Lead poisoning is a stealthy threat to human physiological systems as chronic exposure can remain asymptomatic for long periods of time before symptoms manifest. We presently review the biophysical mechanisms of lead poisoning that contribute to male infertility. Environmental and occupational exposure of lead may adversely affect the hypothalamic-pituitary-testicular axis, impairing the induction of spermatogenesis. Dysfunction at the reproductive axis, namely testosterone suppression, is most susceptible and irreversible during pubertal development. Lead poisoning also appears to directly impair the process of spermatogenesis itself as well as sperm function. Spermatogenesis issues may manifest as low sperm count and stem from reproductive axis dysfunction or testicular degeneration. Generation of excessive reactive oxygen species due to lead-associated oxidative stress can potentially affect sperm viability, motility, DNA fragmentation, membrane lipid peroxidation, capacitation, hyperactivation, acrosome reaction, and chemotaxis for sperm-oocyte fusion, all of which can contribute to deter fertilization. Reproductive toxicity has been tested through cross-sectional analysis studies in humans as well as in vivo and in vitro studies in animals.

Urban stressors and plasmatic 17-β-estradiol (E2) in male exposed workers

The aim of the study is to evaluate if the occupational exposure to urban stressors could cause alterations in 17-β-estradiol (E2) plasma levels and related disorders in male traffic police compared with a control group. After excluding from the study, the subjects with the principal confounding factors, traffic police and controls were matched by age, working life, Body Mass Index (BMI), smoking and drinking habit. A total of 171 male traffic police and 171 controls were included in the study. In traffic police, mean E2 values were significantly lower versus controls ( P < 0.001). The distribution of E2 values in traffic police and controls was significant ( P < 0.001). No significant differences were found in percentage of traffic police versus controls concerning the following questionnaire items: fertility and mental health diseases. Our results suggest that the occupational exposure to chemical urban stressor, interacting with and adding to the psychosocial ones, could alter plasma E2 concentrations in male traffic police compared with a control group. According to our previous researches on other neuro-immune-endocrine parameters, E2 could be used as an early biological marker, valuable for the group, to be used in occupational set even before the onset of the pathologies.

Amino siloxane oligomer-linked graphene oxide as an efficient adsorbent for removal of Pb(II) from wastewater

A high performance sorbent, oligomer-linked graphene oxide (GO) composite, was prepared through simple cross-linking reactions between GO sheets and poly3-aminopropyltriethoxysilane (PAS) oligomers as crosslinking agents. The three-dimensional PAS oligomers prevented GO sheets from aggregation, provided foreign molecules with easier access, and introduced a large amount of amino functional groups. The morphology, structure and property of the PAS-GO composite were determined by scanning electron microscope (SEM), transmission electron microscope (TEM), Fourie transform infrared (FTIR), X-ray diffractometer (XRD), thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS). The adsorption performance of PAS-GO was investigated in removing Pb(II) ions from water. Compared to 3-aminopropyltriethoxysilane functionalized GO (AS-GO) which was prepared by the direct reaction between 3-aminopropyltriethoxysilane and GO, PAS-GO exhibited much higher adsorptivity toward Pb(II) with the maximum adsorption capacity of 312.5mg/g at 303 K and furthermore the maximum adsorption capacity increased with increasing temperature. The adsorption could be conducted in a wide pH range of 4.0-7.0. Importantly, PAS-GO had a priority tendency to adsorb Pb, Cu and Fe from a mixed solution of metal ions, especially from a practical industrial effluent.

Metal toxicity and opportunistic binding of Pb(2+) in proteins

Lead toxicity is associated with various human diseases. While Ca(2+) binding proteins such as calmodulin (CaM) are often reported to be molecular targets for Pb(2+)-binding and lead toxicity, the effect of Pb(2+) on the Ca(2+)/CaM regulated biological activities cannot be described by the primary mechanism of ionic displacement (e.g., ionic mimicry). The focus of this study was to investigate the mechanism of lead toxicity through binding differences between Ca(2+) and Pb(2+) for CaM, an essential intracellular trigger protein with two EF-Hand Ca(2+)-binding sites in each of its two domains that regulates many molecular targets via Ca(2+)-induced conformational change. Fluorescence changes in phenylalanine indicated that Pb(2+) binds with 8-fold higher affinity than Ca(2+) in the N-terminal domain. Additionally, NMR chemical shift changes and an unusual biphasic response observed in tyrosine fluorescence associated with C-terminal domain sites EF-III and EF-IV suggest a single higher affinity Pb(2+)-binding site with a 3-fold higher affinity than Ca(2+), coupled with a second site exhibiting affinity nearly equivalent to that of the N-terminal domain sites. Our results further indicate that Pb(2+) displaces Ca(2+) only in the N-terminal domain, with minimal perturbation of the C-terminal domain, however significant structural/dynamic changes are observed in the trans-domain linker region which appear to be due to Pb(2+)-binding outside of the known calcium-binding sites. These data suggest that opportunistic Pb(2+)-binding in Ca(2+)/CaM has a profound impact on the conformation and dynamics of the essential molecular recognition sites of the central helix, and provides insight into the molecular toxicity of non-essential metal ions.

Reproductive toxicity of metals in men

A combination of genetic, environmental and lifestyle factors contributes to adverse effects on the reproductive health in men. Metals are pervasive in food, water, air, tobacco smoke, and alcoholic beverages. Experimental studies suggest that many metals have adverse effects on the male reproductive function. However, information about reproductive effects of human exposure to metals is scarce and/or inconsistent. This review summarises the information from epidemiological studies of the effects of metal exposure on reproductive function in men. Factors capable of affecting these relationships were identified and discussed. A particular attention is given to the studies considering influence of concomitant exposure to various metals. These studies have generally confirmed that even moderate- to low-level exposure to lead affects certain reproductive parameters, and that exposure to cadmium affects the prostate function and serum testosterone levels. Adverse effects of mercury, manganese, chromium and arsenic on semen quality and altered serum hormone are less well documented. There is no clear evidence that boron exposure may impair reproductive health in men. Only a few studies have investigated reproductive effects of concomitant exposure to several metals and controlled for potential confounders. Future studies should consider the contribution of combined exposure to various metals and/or other factors that may influence individual susceptibility to reproductive health impairment in men.

Flexibility of EF-hand motifs: structural and thermodynamic studies of Calcium Binding Protein-1 from Entamoeba histolytica with Pb2+, Ba2+, and Sr2+

BACKGROUND

EF-hand proteins can be activated by the binding of various heavy metals other than calcium, and such complexes can disturb the calcium-signaling pathway and cause toxicity and disease causing state. So far, no comprehensive study has been done to understand different heavy metals binding to calcium signaling proteins.

RESULTS

In this work, the flexibility of the EF-hand motifs are examined by crystallographic and thermodynamic studies of binding of Pb2+, Ba2+ and Sr2+ to Calcium Binding Protein-1 from Entamoeba histolytica (EhCaBP1). The structures of the EhCaBP1- heavy metal complexes are found to be overall similar, nevertheless specific differences in metal coordination, and small differences in the coordination distances between the metal and the ligands in the metal binding loop. The largest such distances occur for the Ba2+- EhCaBP1 complex, where two bariums are bound with partial occupancy at the EF2 motif. Thermodynamic studies confirm that EhCaBP1 has five binding sites for Ba2+ compared to four binding sites for the other metals. These structures and thermodynamic studies reveal that the EF-hand motifs can accommodate several heavy atoms with similar binding affinities. The binding of Ca2+ to the 1st, 2nd and 4th sites and the binding of Ba2+ to the 1st, 2nd, 4th and 5th sites are both enthalpically and entropically driven, whereas the binding of Sr2+ to the 1st, 2nd and 4th sites are simply enthalpy driven, interestingly in agreement with ITC data, Sr2+ do not coordinate with water in this structure. For all the metals, binding to the 3rd site is only entropy driven.

CONCLUSION

Energetically, Ca2+ is preferred in three sites, while in one site Ba2+ has better binding energy. The Sr2+-coordination in the EF hand motifs is similar to that of the native Ca2+ bound structure, except for the lack of water coordination. Sr2+ coordination seems to be a pre-formed in nature since all seven coordinating atoms are from the protein itself, which also correlates with entropy contributions in Sr2+ binding. These findings improve our understanding of metal association with calcium binding proteins and of metal induced conformational changes.

Semen quality and reproductive endocrinal function related to blood lead levels in infertile painters

Lead causes male reproductive impairment among painters, but information is still limited. Therefore, the effect of lead on semen quality and reproductive endocrinal function in those patients was investigated. A case series of 27 infertile painters were subjected to semen analysis, measuring of blood lead level (PbB) and serum levels of endocrinal parameters including follicle-stimulating hormone (FSH), luteinising hormone (LH), testosterone (T) and prolactin (PRL). Significantly lower sperm count and motility were found in those with duration of exposure (≥ 15 years), but no significant difference was found for PbB and serum levels of FSH, LH, PRL and T. A significant negative correlation between PbB and spermatic count and motility was observed, while there was no significant correlation between PbB and all endocrinal parameters. Patients with PbB ≥ 20 μg dl(-1) showed a significant decrease in sperm motility and increase in testosterone alone among all measured hormones. But the observed decrease in sperm count did not reach a significant level. It is concluded that infertile painters are at risk of lead-related influence on semen quality, especially sperm motility and increased testosterone level without significant affection of other reproductive endocrinal parameters.

Workplace exposures and male infertility - a case-control study

OBJECTIVES

This study examined the association between male infertility and certain occupational exposures.

MATERIAL AND METHODS

A case-control study was carried out from January 2008 to February 2009; on 255 infertile men and 267 fertile men controls. Occupational exposure to certain chemical, physical and psychological workplace hazards was assessed by self-report questionnaire. General and andrological examination was conducted for all participants, however, semen analysis was done only for the infertile men cases, because the fertile men controls refused to give semen samples.

RESULTS

After adjustment of confounders, the results revealed that the following workplace exposure factors significantly increased the risk of male infertility: solvents and painting materials (OR: 3.88, 95% CI: 1.50-10.03), lead (OR: 5.43, 95% CI: 1.28-23.13), VDTs and computers (OR: 8.01, 95% CI: 4.03-15.87), shift work (OR: 3.60, 95% CI: 1.12-11.57) and work-related stress (fairly present: OR: 3.11, 95% CI: 1.85-5.24; often present: OR: 3.76, 95% CI: 1.96-7.52).

CONCLUSION

In spite of the limitations of this study, it supports other studies that raise the attention to minimize the exposure to the workplace hazards that may affect the fertility of male workers.

[Informations for the infertile couple]

The aim of the first consultation related to infertility is supposed to be the optimization of all factors that can increase the chances of pregnancy: more frequent sexual intercourse during the fertility windows; lifestyle modifications (better diet, decreased exposure to tobacco or other toxics); older couples can enjoy the same advice but should be proposed a quicker medical support. Maternal preconceptional advice must be transmitted. A testicular cancer must always be excluded in infertile men, while the risk of hormone-dependent cancers in infertile women remains undetermined. With the results of this first consultation, couples will generally be proposed the best solution to achieve their parental project: ovarian stimulation assisted reproductive technology (IUI, IVF or ICSI) or adoption.

The effect of lead intoxication on endocrine functions

Studies on the effects of lead on the endocrine system are mainly based on occupationally lead-exposed workers and experimental animal models. Although evidence is conflicting, it has been reported that accumulation of lead affects the majority of the endocrine glands. In particular, it appears to have an effect on the hypothalamic-pituitary axis causing blunted TSH, GH, and FSH/LH responses to TRH, GHRH, and GnRH stimulation, respectively. Suppressed GH release has been reported, probably caused by reduced synthesis of GHRH, inhibition of GHRH release or reduced somatotrope responsiveness. Higher levels of PRL in lead intoxication have been reported. In short-term lead-exposed individuals, high LH and FSH levels are usually associated to normal testosterone concentrations, whereas in long-term exposed individuals' low testosterone levels do not induce high LH and FSH concentrations. These findings suggest that lead initially causes some subclinical testicular damage, followed by hypothalamic or pituitary disturbance when longer periods of exposure take place. Similarly, lead accumulates in granulosa cells of the ovary, causing delays in growth and pubertal development and reduced fertility in females. In the parenchyma of adrenals histological and cytological changes are demonstrated, causing changes in plasma basal and stress-mediated corticosterone concentrations and reduced cytosolic and nuclear glucocorticoid receptor binding. Thyroid hormone kinetics are also affected. Central defect of the thyroid axis or an alteration in T4 metabolism or binding to proteins may be involved in derangements in thyroid hormone action. Lead toxicity involves alterations on calcitropic hormones' homeostasis, which increase the risk of skeletal disorders.

Effects on Androstenedione in Male Workers Exposed to Urban Stressors

The aim of this study is to evaluate whether occupational exposure to urban stressors could cause alterations in androstenedione plasma levels in male traffic policemen compared to a control group. After excluding the principal confounding factors, traffic policemen were matched with controls by age, working life, body mass index (BMI), drinking habit, and habitual soy intake in diet. One hundred and ten traffic policemen and 110 controls were included in the study. In male traffic policemen, mean androstenedione values were significantly lower compared to controls. The distribution of androstenedione values in traffic policemen and in controls was significant. Our results suggest that the occupational exposure to chemical urban stressors, interacting with and adding to the psychosocial ones, could alter androstenedione plasma concentrations in traffic policemen compared to a control group. According to our previous research, androstenedione could be used as an early biological marker, valuable for the group to be employed in occupational settings, even before the onset of the endocrine reproductive health diseases.

Structural differences between Pb2+- and Ca2+-binding sites in proteins: implications with respect to toxicity

Pb(2+) is known to displace physiologically-relevant metal ions in proteins. To investigate potential relationships between Pb(2+)/protein complexes and toxicity, data from the protein data bank were analyzed to compare structural properties of Pb(2+)- and Ca(2+)-binding sites. Results of this analysis reveal that the majority of Pb(2+) sites (77.1%) involve 2-5 binding ligands, compared with 6+/-2 for non-EF-Hand and 7+/-1 for EF-Hand Ca(2+)-binding sites. The mean net negative charge by site (1.7) fell between values noted for non-EF-Hand (1+/-1) and EF-Hand (3+/-1). Oxygen is the dominant ligand for both Pb(2+) and Ca(2+), but Pb(2+) binds predominantly with sidechain Glu (38.4%), which is less prevalent in both non-EF-Hand (10.4%) and EF-Hand (26.6%) Ca(2+)-binding sites. A comparison of binding geometries where Pb(2+) has replaced Ca(2+) in calmodulin (CaM) and Zn(2+) in 5-aminolaevulinic acid dehydratase (ALAD) revealed protein structural changes that appear to be unrelated to ionic displacement. Structural changes observed with CaM may be related to opportunistic binding of Pb(2+) in regions of high electrostatic charge, whereas ALAD may bind multiple Pb(2+) ions in the active site. These results suggest that Pb(2+) adapts to structurally-diverse binding geometries and that opportunistic binding may play an active role in molecular metal toxicity.

Plasma 17-alpha-OH-progesterone in male workers exposed to traffic pollutants

The aim of the study is to evaluate if the occupational exposure to urban pollutants could cause alterations on 17-alfa-hydroxy-progesterone plasma levels and related diseases in male traffic policemen. 17-alpha-OH-P is synthesized in Leydig cells and in adrenals; it influences spermiogenesis, acrosoma reaction, testosterone biosynthesis, blocking of gonadotropin secretion; it regulates learning, memory and sleep. After excluding principal confounding factors, i.e., rotating or night shifts, exposure to solvents, paints and pesticides during time-off and smoking, traffic policemen were matched with controls by age, working life and drinking habit. Finally, 112 traffic policemen and 112 controls were included in the study. In traffic policemen 17-alpha-OH-P mean values were significantly higher vs. controls. The distribution of 17-alpha-OH-P values in both groups was significant. An increased frequency of fertility disorders referred to the questionnaire items were found in traffic policemen vs. controls, but the difference was not significant. The occupational exposure to low doses of chemical urban stressor, interacting with and adding to the psychosocial ones, could alter plasma 17-alpha-OH-P concentrations in traffic policemen vs. controls. 17-alpha-OH-P could be used as an early biological marker, even before the onset of the reproductive and mental health diseases.

Bayesian selection of predictors of conception probabilities across the menstrual cycle

There is increasing interest in identifying predictors of human fertility, including environmental exposures, behavioural factors, and biomarkers, such as mucus or reproductive hormones. Epidemiological studies typically measure fecundability, the per menstrual cycle probability of conception, using time to pregnancy data. A critical predictor, which is often ignored in the design or analysis, is the timing of non-contracepting intercourse in the menstrual cycle. In order to limit confounding by behavioural differences between exposure groups, it may be preferable to base inferences on day-specific conception probabilities in relation to intercourse timing. This article proposes Bayesian methods for selection of predictors of day-specific conception probabilities. A particular focus is the case in which data on ovulation timing are not available. We focus on the selection of fertile days in the cycle during which conception probabilities are non-negligible and predictors may play a role. Data from recent European and Italian prospective studies of daily fecundability are presented, and the proposed approach is used to estimate cervical mucus effects within a mid-cycle potentially fertile window using data from the Italian study.

Low blood lead concentration in association with infertility in women

This study investigated the relationship between low-level lead exposure and risk of infertility in women. Study participants consisted of 64 cases recruited at a private infertility clinic and 83 control women from the postpartum clinic unit at a medical center in Kaohsiung, Taiwan. With informed consent, venous blood samples were obtained from subjects, during their early follicular phases (the 1st to 5th days of the menstrual cycle), for measuring concentrations of lead and hormones. Information on other potential risk factors associated with infertility, including reproductive history, Chinese herbal Medicine use, dairy product consumption, residential environment, and sociodemographic status, was obtained during an in-person interview. The mean blood lead level (BLL) in infertile women was significantly higher than that in controls (3.55 vs 2.78 microg/dL, P=0.007). Compared to women with BLL < or = 2.5 microg/dL, women with BLL>2.5 microg/dL were associated with a threefold increased risk for infertility (adjusted odds ratio=2.94, 95% confidence interval 1.18-7.34), after controlling for age, body mass index, smoking, Chinese herbal Medicine use, and irregular menstruation. Women's BLL was a significant predictor of the serum estradiol concentration also. These findings suggest an important role of very low BLL in the risk of infertility in women.

Is inhibin B involved in the toxic effect of lead on male reproduction?

Human studies indicate exposure to lead is associated with decreased sperm quality with modest, if any, effects on conventional reproductive endocrine profile. Inhibin B is a marker of Sertoli cell function and spermatogenesis. The present study evaluates possible effects of lead exposure on serum levels of inhibin B in a group of lead workers as compared with a non-exposed group of hospital personnel. The study population included 68 healthy Belgian workers from a lead smelter (Hoboken, Belgium) and for comparison a control group of 91 hospital personnel (University Hospital Ghent, Belgium). Semen analysis and measurement of current blood lead levels and serum levels of inhibin B, follicle stimulating hormone (FSH) and estradiol (E2). Lead workers had significantly lower sperm concentration (35 vs. 51 million/mL) and higher serum inhibin B (259 vs. 177 pg/mL) as well as lead blood levels 30.9 vs. 3.4 mug/dL) compared with the hospital personnel (all p < 0.05). Serum FSH and E2 levels were similar in both groups. Overall, inhibin B levels correlated significantly positively with blood lead levels and sperm concentration while it was negatively correlated with serum FSH. In multiple regression analysis of data from all participants, blood lead and serum FSH (p < 0.0001 for both) followed by sperm count (p = 0.007) were selected as the only independent variables for inhibin B with an R-adjusted coefficient of determination of 0.3714. The results of the present study suggest that the exposure of the cells of Sertoli to excessive amounts of lead results in inappropriate inhibin B overproduction that may be involved in the impairment of spermatogenesis.

Accuracy of men's recall of their partner's time to pregnancy

BACKGROUND

Occupational studies of fertility often rely on men's report of time to pregnancy (TTP). We assessed accuracy of men's report of TTP compared with TTP derived from data from their female partners.

METHODS

Men from the Dieckmann diethylstilbestrol cohort were interviewed to assess fertility. Men were asked TTP for their most recent pregnancies. Their female partner was subsequently interviewed separately; TTP derived from her data was used as the gold standard. Our analysis was based on 202 couples.

RESULTS

Men's report was identical to the women's-derived TTP in 32% of couples; 74% differed by no more than 2 cycles. Men tended to underestimate TTP (mean difference = -1.2 cycles). Weighted kappa was 0.5 overall and varied by the man's education, the number of pregnancies he had fathered, his stated confidence in reporting, his exposure to diethylstilbestrol, pregnancy planning, and whether he was still married to the index partner.

CONCLUSIONS

Overall accuracy of men's report of TTP was reasonably good, particularly for men who had fathered only one pregnancy.

Teratogen update: lead and pregnancy

This review focuses on the impacts of lead exposure on reproductive health and outcomes. High levels of paternal lead exposure (>40 microg/dl or >25 microg/dl for a period of years) appear to reduce fertility and to increase the risks of spontaneous abortion and reduced fetal growth (preterm delivery, low birth weight). Maternal blood lead levels of approximately 10 microg/dl have been linked to increased risks of pregnancy hypertension, spontaneous abortion, and reduced offspring neurobehavioral development. Somewhat higher maternal lead levels have been linked to reduced fetal growth. Some studies suggest a link between increased parental lead exposure and congenital malformations, although considerable uncertainty remains regarding the specific malformations and the dose-response relationships. Common methodological weaknesses of studies include potential exposure misclassifications due to the frequent unavailability of exposure biomarker measurements at biologically appropriate times and uncertainty regarding the best exposure biomarker(s) for the various outcomes. A special concern with regard to the pregnant woman is the possibility that a fetus might be exposed to lead mobilized from bone stores as a result of pregnancy-related metabolic changes, making fetal lead exposure the result of exposure to exogenous lead during pregnancy and exposure to endogenous lead accumulated by the woman prior to pregnancy. By reducing bone resorption, increased calcium intake during the second half of pregnancy might reduce the mobilization of lead from bone compartments, even at low blood lead levels. Subgroups of women who incurred substantial exposures to lead prior to pregnancy should be considered to be at increased risk.

Neonatal lead exposure changes quality of sperm and number of macrophages in testes of BALB/c mice

BALB/c mice were exposed to 0.1 ppm lead acetate in the drinking water from postnatal day (PND) 1 for 6 weeks. Until PND21, lead exposure was from mother's milk; thereafter, it was directly from the drinking water. The blood lead levels were the highest in pups before weaning (59.5+/-0.9 microg/dL) and significantly lower between PND21 and PND42 (20.3+/-4.7 microg/dL). At PND42, lead-exposed male mice were tested for fertility, sperm DNA, and macrophage number. Mating of lead-treated males with non-treated females confirmed the reduction of fertility in the exposed males. Flow cytometric studies of testicular preparations indicated that the sperm count was not different between lead-exposed and control males; however, the lead-treated mice had a significant increase in the number of testicular cells having a < 1n amount of DNA, which coincided with a decrease in the number of testicular cells with a 2n and 4n amount of DNA. The number of testicular macrophages also was decreased in lead-exposed males, which could reflect altered levels of CSF-1 or response to CSF-1, as previously reported [Kowolenko, M., Tracy, L., Lawrence, D.A., 1989. Lead-induced alterations of in vitro bone marrow cell responses to colony stimulating factor-1. J. Leukoc. Biol. 45, 198-206]. Our study showed that exposure to 0.1 ppm of lead during the neonatal and adolescent period is sufficient to reduce fertility in adult male mice; however, it did not affect sperm count on PND42. The presence of an increased number of apoptotic (< 1n amount of DNA) testicular cells may be diagnostic of defective sperm function. Thus, an administered dose of 0.1 ppm via drinking water ingestion by neonatal male BALB/c mice sufficient to produce PbB of 20-60 mg/dL compromised reproductive function in these mice as adults.

Decreased fecundity among male lead workers

AIMS

To investigate time to pregnancy (TTP) in male lead workers in order to determine the dose-response relation between blood lead and decreased fecundity.

METHODS

A total of 163 currently employed married male lead battery workers were classified into five categories of exposure based on questionnaire information and annual individual blood lead measurement. Information pertaining to the TTP was collected using personal interviews with 133 men and their spouses, with 280 valid pregnancies. The fecundability ratios (FRs) were calculated with the Cox discrete proportional hazard regression technique to evaluate the effects of lead exposure.

RESULTS

After other factors associated with TTP were controlled for, there was a dose-response relation between blood lead level and TTP. The measured FRs were 0.90 (95% CI 0.61 to 1.34), 0.72 (0.46 to 1.11), 0.52 (0.35 to 0.77), and 0.40 (0.27 to 0.59) for concurrent blood lead levels of <20, 20-29, 30-39, and > or =40 microg/dl, respectively. Paired self comparison was also performed for 41 couples that had pregnancies prior to lead exposure and pregnancies with male occupational lead exposure. The TTP was prolonged for 0.15 cycles by a 1 microg/dl increase in blood lead.

CONCLUSIONS

These results corroborate the hypothesis that a raised blood lead level affects fecundity. A blood lead level of less than 40 microg/dl may still significantly prolong TTP.

Parental lead exposure and total anomalous pulmonary venous return

BACKGROUND

Investigators from the Baltimore-Washington Infant Study (BWIS) reported an association between self-reported maternal lead exposure and total anomalous pulmonary venous return (TAPVR) in their offspring. This association was further evaluated in the BWIS population using a more sensitive exposure estimate.

METHODS

Cases included 54 live-born infants with TAPVR; controls were a stratified random sample of 522 live-born infants from the BWIS control group. Parental lead exposure was based on three assessment methods, including: an industrial hygiene assessment, an a priori job exposure matrix, and self-reported exposures. A parent was classified as exposed to lead if he/she was classified as exposed by any one of the assessment methods.

RESULTS

Approximately 17% of case mothers and 11% of control mothers were classified as exposed to lead during the three months prior to conception through the first trimester (odds ratio [OR], 1.57; 95% confidence interval [CI], 0.64-3.47). Among fathers, 61% of case fathers and 46% of control fathers were classified as exposed to lead during the six months prior to conception (paternal critical period) (OR, 1.83; 95% CI, 1.00-3.42). During the paternal critical period, when only the father was exposed compared to neither parent exposed, the OR for any lead exposure and TAPVR was 1.65 (95% CI, 0.84-3.25).

CONCLUSIONS

This study supports a possible association between paternal lead exposure and TAPVR. Further studies are warranted using validated assessment methods for occupational and nonoccupational lead exposures to corroborate this association and to elucidate the possible biological mechanism. Birth Defects Research (Part A), 2004.

Adverse haematological outcome and environmental lead poisoning

The South-eastern Area (SA) of the Municipality of La Spezia (Liguria Region, Italy) is characterised by a heavy environmental lead (Pb) contamination, chiefly due to the emissions of a Pb-processing plant in operation since 1930. In order to assess the risk of Pb poisoning of residents of SA, and to estimate the degree of association between the blood Pb level (BLL) and haematocrit % (HCT), intended as a biomarker of early haematological dysfunction, we reanalysed data of 785 individuals collected in 1992 as a part of a larger national biological monitoring project. Multiple normal regression modelling was applied to estimate the role of residence on log-transformed BLL, and Median Ratio (MR) was used as an index of effect. The same statistical modelling was also applied to reveal the relationship between HCT and BLL. Allowing for several confounders (including occupational exposure to Pb), residents of SA showed a 14% increase (MR=1.14, 95% IC=1.06-1.23%) in the median BLL value compared to people living outside SA. The excess reached 27% (MR=1.27, 95% IC=1.14-1.41%) after 30 years of residence. Parallel results were also obtained in a subgroup composed only of pupils (<18 years, non-smokers, non-drinkers). Finally, regression analysis highlighted a statistically significant parabolic trend in HCT in relation to BLL. The non-linear dose-response relationship, which attests to an adverse effect on the erythrocytic function of BLLs at least over 17.00 microg/dl, is in agreement with the findings of other authors and consistent with the results of an excess occurrence of self-reported anaemia obtained from a previous comparative survey carried out on the same population.

Methodologic and statistical approaches to studying human fertility and environmental exposure

Although there has been growing concern about the effects of environmental exposures on human fertility, standard epidemiologic study designs may not collect sufficient data to identify subtle effects while properly adjusting for confounding. In particular, results from conventional time to pregnancy studies can be driven by the many sources of bias inherent in these studies. By prospectively collecting detailed records of menstrual bleeding, occurrences of intercourse, and a marker of ovulation day in each menstrual cycle, precise information on exposure effects can be obtained, adjusting for many of the primary sources of bias. This article provides an overview of the different types of study designs, focusing on the data required, the practical advantages and disadvantages of each design, and the statistical methods required to take full advantage of the available data. We conclude that detailed prospective studies allowing inferences on day-specific probabilities of conception should be considered as the gold standard for studying the effects of environmental exposures on fertility.

Time To Pregnancy and occupational lead exposure

BACKGROUND

Lead exposure is known to be harmful to the male reproductive system, including impairment of fertility. However, it is unclear whether currently existing low levels of exposure have this effect.

AIMS

To study retrospectively current workers in lead using industries (battery manufacture, smelting, etc), and in non-lead using control industries, in four European countries, with Time To Pregnancy as the outcome variable, as part of the EU funded Asclepios Project.

METHODS

Exposure assessment was mainly by blood lead values, which were available from the late 1970s, supplemented by imputed values where necessary. Three exposure models were studied: (1) short term (recent) exposure; (2) total duration of work in a lead using industry; and (3) cumulative exposure. A Cox proportional hazards model with discrete ties was used for the statistical analysis, with covariates for both partners.

RESULTS

A total of 1104 subjects took part, of whom 638 were occupationally exposed to lead at the relevant time. Blood lead levels were mainly less than 50 microg/dl. No consistent association of Time To Pregnancy with lead exposure was found in any of the exposure models, although reduced fertility was observed in one category each in models (2) and (3).

CONCLUSIONS

This basically negative result is unlikely to be due to the misclassification of key variables, to insufficient statistical power, or to bias, for example, response bias. If any impairment of male reproductive function exists at the levels of occupational lead exposure now current, it does not appear to reduce biological fertility.

Biomarkers for male reproductive health hazards: are they available?

This review aims to give an overview of some of the biomarkers that have been used for the monitoring of human exposure to xenobiotics as well as to provide a summary of some of the recent epidemiological studies on male reproductive health of exposure to environmental and occupational toxicants. Possible molecular mechanisms on seminal quality change are also suggested. Studies using various biomarkers have no doubt enabled us to better characterize the effect of environmental pollutants on the male reproductive system. However, the sensitivity and specificity of these biomarkers have not been comprehensively validated. Furthermore, many epidemiological findings are difficult to replicate owing to the inherited methodological problems of male reproductive health investigations, such as the small number of study subjects, low compliance rate, substantial intra-individual variability in semen parameters, measurement techniques and misclassifications based on single assay. Oxidative damage, in particular DNA-damage caused by free radicals, generated either by xenobiotics, or endogenously, is now thought to be a key molecular mechanism associated with semen quality and sperm function. Laboratory studies and epidemiological findings have suggested that the male reproductive system is susceptible to reactive oxygen species (ROS). On the other hand, there is so far no single all-encompassing biomarker of reproductive capacity in men. A panel of biomarkers with specific goals should be considered. Collaborative multidisciplinary studies are also needed to overcome some of the issues mentioned here.