Study Of Variability In Urinary Metal Levels And Exposure To Metals At Environmental Levels In Relation To Male Reproductive Health

Part One Variability of metal levels in spot,first morning,and 24-hour urine samples in healthy adult menObjectives:To investigate the variability of metal levels in spot,first morning,and 24-hour(hr)urine collections over a 3-month period.Methods:Eleven healthy non-smoking adult men were asked to provide every spot urine samples(n=529)on days 0,1,2,3,4,30,60,and 90 during the 3-month period.The urinary levels of 18 metals(aluminum,chromium,manganese,iron,cobalt,nickel,copper,zinc,arsenic,selenium,molybdenum,cadmium,tin,antimony,tungsten,thallium,lead and uranium)were measured using inductively coupled plasma-mass spectrometry.The intraclass correlation coefficients(ICCs)were calculated to assess the reproducibility of metal measures in the 3 types of voids(i.e.,spot,first morning and 24-hr urine collections)and the sensitivity and specificity were computed to evaluate how well single or repeated sample collections determined the individuals' 3-month average exposure.Results:Fair-to-good reproducibility was observed for the serial measurements of Cd(ICCs>0.40)in the three sample types over the 3-month period,whereas the serial measurements of aluminum,chromium,manganese,iron,cobalt,nickel,copper,zinc,arsenic,selenium,molybdenum,antimony,tungsten,thallium,lead and uranium showed poor reproducibility(ICCs<0.40).Use of single spot or first morning urine samples to classify the high(top 33%)3-month average metal levels had uniformly high specificities(0.70-0.84)but relatively low sensitivities(0.40-0.57),except for Cd(0.77).The sensitivities and specificities increased when repeated samples were randomly collected from each participant.Conclusions:Urinary levels of aluminum.chromium,manganese,iron,cobalt,nickel,copper,zinc,arsenic,selenium,molybdenum,tin.antimony,tungsten,thallium,lead and uranium varied greatly over a 3-month period and the use of single spot samples to classify an individuals' 3-month average exposure can result in a moderate degree of exposure misclassification.Collection of multiple samples from each participant is an option for reducing exposure classification errors.Part Two Associations of urinary metal levels with semen quality,sperm DNA integrity and spermatozoa apoptosisObjectives:To investigate the associations between environmental metal exposure and semen quality,sperm DNA integrity and spermatozoa apoptosis,using repeated measurements of urinary metals as biomarker of exposure.Methods:A total of 1052 men were recruited from the Reproductive Center of Tongji Hospital from March to June 2013.Each man provided a semen sample and two urine samples.Semen quality parameters,sperm DNA integrity,spermatozoa apoptosis and urinary concentrations of 18 metals(aluminum,chromium,manganese,iron,cobalt,nickel,copper,zinc,arsenic,selenium,molybdenum,cadmium,tin,antimony,tungsten,thallium,lead and uranium)were determined.Associations of these metals with semen quality parameters(n= 1052),DNA integrity measures(n=516)and spermatozoa apoptosis makers(n=460)were assessed using confounders adjusted linear or logistic regressions.Results:After adjusting for multiple comparisons and various elements,urinary cadmium was inversely associated with progressive and total sperm motility(both P<0.02)in multivariable linear regressions,consistent with the trends of increased odds ratios for below-reference semen quality parameters observed in the logistic models(both P<0.05).Additionally,urinary arsenic was inversely associated with progressive and total sperm motility,molybdenum and lead was inversely associated with percentages of normal sperm morphology,and iron was inversely associated with percentage of PI+ spermatozoa,whereas manganese was positively associated with percentage of Annexin V+/PI-spermatozoa(all P<0.10).These relationships were confirmed when modeling these metals as continuous variables in spline models.Conclusions:Elevated cadmium and arsenic exposure may be associated with reduced sperm motility,and molybdenum and lead exposure may contribute to increased sperm morphology,manganese may induce spermatozoa apoptosis,whereas iron may be beneficial for living spermatozoa.Part three Relationships between seminal plasma metals and semen quality,sperm DNA integrity and spermatozoa apoptosisObjectives:To determine the association between seminal plasma metals and semen quality,sperm DNA integrity and spermatozoa apoptosis.Methods:The concentrations of 18 metals(aluminum,chromium,manganese,iron,cobalt,nickel,copper,zinc,arsenic,selenium,molybdenum,cadmium,tin,antimony,tungsten,thallium,lead and uranium)were determined in the seminal plasma of 746 men from Part two who had adequate semen samples.Multivariable linear or logistic regression models were used to assess the association of these metals with semen quality(n=746),sperm DNA integrity(n=404)and spermatozoa apoptosis(n=331).Results:After adjusting for multiple comparisons and various elements,we found inverse dose-response relationships between seminal plasma arsenic levels and progressive and total sperm motility,which were in accordance with the trends for increased ORs for below-reference semen quality parameters in the logistic models.We also found inverse relationships for cadmium levels with progressive and total sperm motility,whereas positive correlations between zinc and sperm concentration,between copper and arsenic and the percentage of tail DNA,between arsenic and selenium and tail length and tail distributed moment,and between tin and the percentage of PI+spermatozoa(all P for trend<0.05).These relationships were further confirmed in cubic spline models.Conclusions:Elevated cadmium and arsenic exposure may be associated with reduced sperm motility.Copper,arsenic and selenium exposure may cause sperm DNA damage,and tin may induce cell death,whereas Zn may be beneficial to sperm concentration.