A survey of semen indices in insecticide sprayers

This study aims at clarifying the semen indices of insecticide sprayers who are exposed mainly to organophosphorus and pyrethroid insecticides. Eighteen male sprayers out of 54 working for 9 companies in central Japan and 18 age-matched students or medical doctors as unexposed controls participated in detailed reproductive check-ups conducted in summer and the following winter. The sprayers were exposed to insecticides more in summer, the busiest season, than winter, the off-season (p<0.05). Erythrocyte true cholinesterase activities in the sprayers were lower than in the controls in summer (p<0.05), and decreased in significant association with the increase in exposure frequency. Testicular volumes in the sprayers tended to be smaller than in the controls (p=0.06). The serum testosterone concentration in winter in the sprayers was higher than in the controls (p<0.05), though luteinizing hormone and follicle stimulating hormone concentrations were not significantly different. The sperm counts and vitality were comparable between the groups, but detailed sperm motility analysis in summer revealed that the percentages of slow progressive and nonprogressive motile sperm were twice as high in the sprayers (p<0.05), and that of rapid progressive sperm tended to be lower (p=0.06). Such differences were not observed in winter. Differential sperm morphology counts showed that interaction of group and abstinence effects were significant in sperm with normal morphology and with head deformity only in the summer check-up. Despite possible inherent differences between the groups, the above season-dependent differences suggested that the observed lower semen quality in the sprayers was associated with pesticide spraying work.     

Temporal trends in bull semen quality: A comparative model for human health?

Introduction

A decline in human semen quality over the past 30-60 years has been reported in numerous epidemiological studies from the United States and Europe. We evaluated temporal trends in semen quality parameters in dairy bulls. The long-term management of dairy bulls for artificial insemination presented a unique opportunity to evaluate temporal trends in semen quality and explore this relationship as a potential animal model for reproductive abnormalities in humans.

Materials and methods

Bull semen analysis data from 1965 through 1995 were collected from a large artificial insemination organization. Semen analyses from 12- to 18-month-old Holstein dairy bulls were included in the study and consisted of daily sperm concentration, daily ejaculate volume, total daily sperm output, percentage of sperm with normal morphology, and percentage of sperm with normal post-thaw motility. Multiple regression analysis, logistic regression, and general linear modeling were used to determine temporal trends over the 30-year period.

Results and discussion

Semen quality appears to have declined from 1970 to 1980 or 1985 as manifested by declines in daily ejaculate volume, daily sperm concentration, and total daily sperm output. In contrast, sperm morphology and motility improved over the same period. In approximately 1980 or 1985, depending on the parameter, ejaculate volume, sperm concentration, total sperm, and motility improved. However, normal morphology began to deteriorate during this same period. Methodological inconsistencies over time introduce uncertainty in analyses of temporal trends in semen quality in this and previous human studies. However, changes in technology do not appear to be solely responsible for the temporal trends observed. The source of the decline in semen quality in the bulls studied is unknown. If the decline in semen quality were due to exposure to endocrine disrupting chemicals, then a continued decline or a leveling-off would be expected. Instead, a rise in semen quality was observed during the latter portion of the observation period.     

男性不育患者精子形态及质量与精液白细胞的关系

目的探讨男性不育患者精子形态及质量与精液白细胞的关系。方法随机选取202例男性不育患者的精液,严格按照WHO人类精液实验手册要求检测精液质量、形态及精液中的白细胞。结果 202例不育患者中有58例（占28.7%）精液中的白细胞〉1×106个/ml,设为白细胞精子组,其余144例（占71.3%）患者精液中白细胞≤1×106个/ml,设为非白细胞精子组。白细胞精子症组患者精液与非白细胞精子症组患者比较在精子密度、精子活动率方面明显降低,液化时间明显增加（P〈0.05）;白细胞精子症组形态正常精子所占比例明显低于非白细胞精子症组（P〈0.05）,并且精液白细胞与正常形态精子率呈显著负相关（P〈0.05）。结论男性不育患者的精液白细胞增多影响精子质量和精子形态的正常。     

Semen collection, characterisation and artificial insemination in the beluga (Delphinapterus leucas) using liquid-stored spermatozoa

Ejaculates were collected from a beluga (Delphinapterus leucas) to gain an understanding of sperm biology and develop a short-term sperm preservation method for use in artificial insemination (AI). Ejaculate parameters and biochemistry, semen production and serum testosterone concentrations of an adult male were characterised for 21 months. Sperm viability, acrosome integrity and morphology did not change (P > 0.05) but ejaculate volume, sperm concentration and total spermatozoa per ejaculate were higher (P < 0.05) from January to June than from July to December. Peak testosterone concentrations (P < 0.05) were observed from October to April (8.0 +/- 1.6 ng mL(-1)). The effects of hyaluronic acid (HA), antioxidants, storage temperature and time on in vitro sperm characteristics were examined. Motility parameters and viability were improved (P < 0.05) when semen was stored at 5 degrees C compared with 21 degrees C. During the first 24 h of storage sperm agglutination was absent only at 5 degrees C in the presence of HA. A nulliparous 28-year-old female was inseminated endoscopically with liquid-stored semen. A pregnancy and birth of a calf was achieved following AI for the first time in this species, thereby validating both the AI technique and the fertility of beluga spermatozoa after chilled storage in a specialised diluent.     

影响精液质量的因素

精液异常是男性不育的主要指征,拥有健康精液是优生优育的重要保证,随着科学技术的发展,各种影响生育的不良因素被逐渐认识。据报道,近几年我国育龄男性精液质量异常人数呈上升趋势,有关人员曾对此做过研究和统计,其中包括对一次性射精量、精液黏稠度、精液液化时间、以及精子总数、精子密度、正常精子形态、精子运动情况和精子成活率、活动率等,通过流行病学调查分析认为,造成精液异常的主要原因除年龄因素之外,物理因素、化学因素、生物因素、营养因素、病理因素以及不良的生活习惯都有可能对其产生影响。参照WHO标准,结合我国相关调查,总结造成育龄男性精液异常的各种原因,对确保精液质量的健康大有意义。因此,加强对环境的保护,调整生活方式,保持良好的身体状态十分重要。     

Semen quality and reproductive health of young Czech men exposed to seasonal air pollution

This study of male reproductive health in the Czech Republic resulted from community concern about potential adverse effects of air pollution. We compared young men (18 years of age) living in Teplice, a highly industrialized district with seasonally elevated levels of air pollution, to those from Prachatice, a rural district with relatively clean air. Surveys were scheduled for either late winter, after the season of higher air pollution, or at the end of summer, when pollution was low. Participation included a physical examination, donation of a semen sample, and completion of a questionnaire on health, personal habits, and exposure to solvents and metals through work or hobby. Analysis of data from 408 volunteers showed that the men from Teplice and Prachatice were similar in physical characteristics, personal habits, and work- or hobby-related exposures. Sixty-six percent (272) of these men donated a single semen sample for routine semen analysis, computer-aided sperm motion analysis, and sperm chromatin structure assay. The mean (median) sperm concentration and sperm count were 61. 2 (44.0) million/mL semen and 113.3 (81.5) million, respectively, and were not associated with district of residence or period of elevated air pollution. However, periods of elevated air pollution in Teplice were significantly associated with decrements in other semen measures including proportionately fewer motile sperm, proportionately fewer sperm with normal morphology or normal head shape, and proportionately more sperm with abnormal chromatin. These results suggest that young men may experience alterations in sperm quality after exposure to periods of elevated air pollution, without changes in sperm numbers.     

分段射精法收集少精子症患者精液质量比较

目的:探讨分段射精法在精子优选过程中的有效性。方法:采用分段射精法收集少精子症患者前后两部分精液,分别检测前后两部分精液的精子参数。结果:前部分精液的精子密度、精子活动率、精子形态和精子顶体完整性均显著高于后部分,而精子存活率、精子膜的完整性前后两部分无显著差异(P>0.05)。结论:对于少精子症患者,采用分段射精法优选精子,能有效改进精子的质量参数,提高精液中精子密度、精子活动率、正常形态精子和正常顶体精子比例。     

Seasonal patterns of LH, testosterone and semen quality in the Northern pintail duck (Anas acuta)

This study characterized seasonal changes in circulating LH and testosterone and in semen production and quality in the Northern pintail duck. Plasma LH and testosterone were measured in blood samples collected weekly throughout the year from eight males exposed to natural fluctuations in day length and temperature. Semen quality was evaluated weekly in these same males from April-June, the months when spermatozoa were produced. Semen quality (based on sperm concentration and normal morphology) peaked 0-2 weeks after sperm production onset and decreased sharply before sperm production cessation in late June. Nadir LH concentrations were measured in July and August with peak LH observed in May and November. There were clear seasonal patterns in circulating testosterone with July-September values being less (P<0.05) than October-December which, in turn, were less (P<0.05) than January-March. Maximal circulating testosterone (P<0.05) occurred during April-June, coincident with semen production. Weekly circulating LH during the breeding season was directly related to testosterone concentrations (P<0.01), but was not correlated to any specific semen or sperm trait (P>0.05). Testosterone concentrations throughout the breeding season were correlated (P<0.05) to total numbers of spermatozoa produced (volume x cell concentration) and percent normal sperm morphology. In summary, the Northern pintail experiences seasonal hormone fluctuations, with maximum circulating testosterone coinciding with peak ejaculate quality reflected by the production of high numbers of morphologically normal spermatozoa.     

Effect of carbosulfan pesticide and selenium on some semen characteristics and serum testosterone in male rabbits

This study was undertaken to investigate the hazardous effects of carbosulfun pesticide on the level of serum testosterone and on semen quality in male New Zealand rabbits, and to determine whether selenium can alleviate these effects when given to the treated animals. Carbosulfan was given orally to animals in two doses (1/100 LD50 and 1/10 LD50 per kg body weight) weekly, while selenium (0.3 mg per kg body weight) was given alone or in combination with carbosulfan. The experiment was divided into three periods of 6 weeks each as follows: preliminary, treatment and recovery. Semen and blood samples were collected weekly and biweekly throughout experiment, respectively. Semen analyses indicated significant decreases in ejaculate volume, sperm concentration, total sperm output, sperm motility and fructose content. This was associated with a significant decline in the level of serum testosterone in the treated animals. Meanwhile pesticide treatment caused increases in the percentages of abnormal and dead spermatozoa, sperm without acrosomes and methylene-blue reduction time. Selenium combined with carbosulfan reduced the detrimental effects of the pesticide in most of the measured parameters.     

生活工作方式对中国年轻男性精液质量影响的调查研究

目的:研究中国婚检人群中正常年轻男性的精液质量与生活工作方式关系。方法:以问卷形式调查对象一般人口学特征、职业暴露以及工作和生活方式。手淫法采集精液做常规精液分析。对生活工作方式与精液质量指标之间的关系进行非参数比较(wilcoxon秩和检验以及spearman等级相关分析);将精液参数按四分位数划分为4个等级,进行有序多分类的Logistic多因素分析。结果:多因素Logistic分析显示坐姿工作对男性精液质量有不良影响,与非坐姿工作相比,使精子密度降低的可能性较大,可能影响精子存活率及前向运动率。经常清洗外生殖器是精液量降低的保护性因素,经常穿紧身裤可能是精液量下降的危险因素,洗澡的水温较热,睡电热毯等生活方式也会影响精液质量。装修居室增加精子计数降低的危险性,精神紧张对精液质量尚无负面影响。结论:坐姿工作、清洁习惯等生活和工作方式对男性的精液质量可能有很大影响,养成良好的清洁习惯,避免和减少可致阴囊温度升高的生活、工作方式是提高精液质量,促进男性生殖健康的重要途径。     

Effect of STS 557 on semen composition, fertility and sexual behaviour of male rabbits

Fertility control of male rabbits was achieved by daily oral administration of STS 557 (17-cyanomethyl-17β-hydroxy-estra-4.9(10)-diene-3-one) over a period of 8 weeks. In doses of 10 and 20 mg STS 557 per animal per day, fertility inhibition was accompanied by a decrease of mean number of mounts and ejaculations. Furthermore, semen volume, number of sperm per ejaculate, and sperm motility were reduced. At a dose of 5 mg STS 557 per day, male sterility was associated with reduction of sperm motility and semen fructose content. Libido, semen volume, sperm number, and sialic acid content in semen remained unaffected. Development of male contraceptives on the basis of chronic progestin treatment without concomitant androgen supplement may thus be possible.     

大学生生殖健康状况分析

目的评估大学生供精志愿者的精液质量,了解大学生的生殖健康状况。方法按照2003年国家卫生部修订的《人类精子库基本标准和技术规范》的筛查程序,对355例在校大学生供精志愿者的精液进行分析。结果37名（10.4%）供精志愿者达到卫生部供精质量标准,共淘汰供精者318人（89.6%）,其中因精液初筛质量不达标准267人（75.2%）,因健康体检不合格26人（7.4%）,未取出精液4人（1.1%）,精液质量正常未来体检9人（2.5%）,精子正常形态率〈30%者6人（1.7%）,冷冻复苏率（a＋b）级〈60%者6人（1.7%）。供精志愿者的精液质量达到WHO正常男性生育参数者135人（38.0%）。结论供精志愿者的精液质量降低,大学生的生殖健康应引起全社会的关注。     

Changes in the Quality of Rabbit Semen in 14 Consecutive Ejaculates Obtained Every 15 Minutes

Modifications of semen quality related to ejaculation frequency is one of the most important and neglected factors from the standpoint of artificial insemination or sperm competition. New Zealand white rabbits ( Oryctolagus cuniculus ) offer an advantageous experimental model because they have characteristic sexual behavior, they present rapid ejaculation after a single intromission, they have a very short interval between successive ejaculations, and semen can be easily collected. The authors studied the modifications on sperm quality (semen volume, sperm concentration, sperm motility) produced by 14 consecutive ejaculations recovered every 15 min using stimulus females and an artificial vagina. Bucks were exposed every 15 min to a sexually receptive female. After each ejaculation the female was removed and reintroduced 15 min later. Sperm concentration showed a clear biphasic conduct. The amount of spermatozoa per milliliter decreased rapidly until ejaculate number 6, showed a highly significant increase in ejaculates 7-9, and decreased to nil in the last 2 ejaculates. Total number of ejaculated spermatozoa was 557 &#50 10 6, 76% of which were recovered from the first 4 ejaculates. Ejaculate volume also showed a biphasic conduct. In the first ejaculates the volume decreased linearly until ejaculate number 6, showed a significant increase in ejaculates 7-10, and then decreased. The total semen volume recovered during the experiment was 2.44mL, 40% of which (0.98mL) was recovered from the first 2 ejaculates. Individual motility in the first 6 ejaculates was preferentially progressive (60% of the sperms) and turned to random or in situ from the seventh ejaculate up. The proportion of spermatozoa with cytoplasmic droplets increased from ejaculates 6 and 7 up. The results seem to reflect an acceleration of semen transport through the epididymis when the demands for spermatozoa increase.     

Ovarian activity in Arabian leopards (Panthera pardus nimr): sexual behaviour and faecal steroid monitoring during the follicular cycle, mating and pregnancy

The Arabian leopard is a critically endangered subspecies endemic to the Arabian Peninsula. A fundamental understanding of the ovarian activity of the leopard is important to enhance the success with which it breeds in captivity. The objective of the present study was to characterise the endocrinology of the follicular cycle, ovulation and pregnancy in captive females using faecal steroid hormone analyses and observations of sexual behaviour. The follicular cycle of the leopard was shown to last 18-23 days based on the interval between consecutive peaks of faecal oestrogen conjugates, and the occurrence of silent heats was high. Puberty had commenced at 2 years of age, but faecal steroid profiles did not match those of the adult female until 3 years of age. No seasonal change in ovarian steroid excretion was observed, although behavioural oestrus was suppressed in summer. Significant rises in faecal progestagen concentrations were only recorded in mated leopards, indicating that these females were strictly induced ovulators. However, only 60% of these mating periods were ovulatory. Progestagen concentrations during pregnancy were significantly higher than those of the non-pregnant luteal phase. The average duration of the non-pregnant and pregnant luteal phases was 39 and 97 days, respectively. The basic features of the reproductive cycle of the Arabian leopard described here form an important foundation for further study into its reproduction.     

A short-term evaluation of semen and accessory sex gland function in phase III trial subjects receiving intravasal contraceptive RISUG

Following the intravasal injection of a new male contraceptive RISUG (reversible inhibition of sperm under guidance) in volunteers, routine semen analysis, semen biochemistry and germ cell morphology were evaluated in comparison with the corresponding preinjection samples for a maximum period of 6 months. Sperm counts in all 25 subjects before injection varied from 45 to 120 x 10(6)/ml. Out of 25 subjects, 6 became azoospermic after 1 month, 15 after 2 months, 3 after 3 months and 1 after 4 months of contraceptive injection. The mean volume of the ejaculates was found to be less as compared to preinjection samples. Occasional sperm or sperm heads and immature germ cells were identified in only a few postinjected subjects. However, no pregnancy was reported in these subjects during the study period. Abnormal morphology found in most of the sperm, but not in the accompanying immature germ cells, may be due to a charge-related effect on the former but not on the latter cells. Neutral alpha-glucosidase, the biochemical marker for epididymis, was estimated to be significantly lower in the seminal plasma of all the postinjected subjects. On the other hand, acid phosphatase activity and fructose levels in the seminal plasma were found to be in the normal range. Based on the above findings, it is concluded that at least for the present study period, RISUG, a new male contraceptive, is effective as a partially occluding agent in the vas deferens.     

Ejaculate traits in the Namibian cheetah (Acinonyx jubatus): influence of age, season and captivity

The objective was to examine the influence of animal age, season and captivity status on seminal quality in wild-born cheetahs (Acinonyx jubatus) in Namibia, Africa. Animals were divided into three age categories: juvenile (14-24 months; n = 16 males, 23 ejaculates); adult (25-120 months; n = 76 males, 172 ejaculates); and aged (>120 months; n = 5 males, 5 ejaculates). Seasons were categorised into hot-wet (January-April), cold-dry (May-August) and hot-dry (September-December). A comparison between freshly wild-caught (n = 29 males, 41 ejaculates) and captive-held cheetahs (n = 68 males, 159 ejaculates) was also conducted. Raw ejaculates contained 69.0 +/- 1.1% motile spermatozoa (mean +/- s.e.m.) with 73.6 +/- 1.5% of these cells containing an intact acrosome. Overall, 18.4 +/- 0.9% of spermatozoa were morphologically normal, with midpiece anomalies being the most prevalent (approximately 39%) defect. Juvenile cheetahs produced ejaculates with poorer sperm motility, forward progressive status, lower seminal volume and fewer total motile spermatozoa than adult and aged animals. Spermatogenesis continued unabated throughout the year and was minimally influenced by season. Proportions of sperm malformations were also not affected by season. Ejaculates from captive cheetahs had increased volume and intact acrosomes, but lower sperm density than wild-caught counterparts. In summary, Namibian cheetahs produce an extraordinarily high proportion of pleiomorphic spermatozoa regardless of age, season or living (captive versus free-ranging) status. Young males less than 2 years of age produce poorer ejaculate quality than adult and aged males. Because (1) all study animals were wild born and (2) there was little difference between freshly caught males and those maintained in captivity for protracted periods, our results affirm that teratospermia in the cheetah is mostly genetically derived. It also appears that an ex situ environment for the Namibian cheetah can ensure sperm quality comparable with that for free-living males.     

中国年轻男性精液质量与血清重金属含量的典型相关分析

目的:了解中国年轻男性的精液质量与血清重金属含量的相关关系。方法 研究对象为1998年12月至1999年12月在上海、河南、浙江、山西、青岛、河北、贵州七省市妇保所进行婚检的正常男性志愿者529例。结果 调整地区因素后铅、镉与正常形态精子率存在负相关；但精液质量与血清重金属两组指标间的典型相关关系不明显。有两个省(河南、贵州)的典型相关分析结果有显著性，显示镉含量对正常形态精子率有不良影响；锰对精液质量的影响不明显；精子数量指标与血清重金属的关系不明显；河南的结果还表明铅影响精子的存活和形态。结论 总体而言，精液质量与血清重金属之间的典型相关关系不明显。但局部地区典型相关分析发现血清铅、镉可能对精子质量有不良影响．     

Environmental organochlorines and semen quality: results of a pilot study

There have been numerous studies that suggest that sperm concentrations (sperm counts) are declining in men. However, other studies suggest that sperm counts are not declining or may be increasing in some areas. Although there is disagreement on whether there is a downward temporal trend in sperm counts, the studies provide evidence that sperm counts vary by geographic location. It has been hypothesized that the geographic variation in sperm concentrations may be due to environmental exposures, lifestyle factors, or some unknown causes. To determine whether contemporary ambient levels of polychlorinated biphenyls (PCBs) and p,p-DDE are associated with altered semen quantity and quality, we selected a study population without specific exposure to PCBs or p,p-DDE. The present study presents the results from a pilot study on the relationship between serum PCBs and p,p-DDE and semen quality in 29 subjects recruited from the Massachusetts General Hospital Andrology Laboratory. Of the 29 subjects, 3 had sperm concentrations < 20 million/mL, 7 had < 50% motile sperm, 9 had < 4% normal morphology, and 6 were below normal in more than one semen parameter. The 18 subjects with normal spermatozoa concentration, motility, and morphology were used as comparison subjects. The mean (SE) concentration of the sum of PCBs and p,p-DDE was 242 ng/g lipids (34.0) and 354 ng/g lipids (120), respectively, for men with below normal motility as compared to 202 ng/g lipids (16.6) and 240 ng/g lipids (31.1), respectively, for the comparison subjects. The data showed general trends that were suggestive of an association between PCBs and p,p-DDE and abnormal motility, as well as with sperm concentration and morphology. A full-scale study is currently in progress.     

Improvement in human semen quality after oral supplementation of vitamin C

This study was carried out to monitor the effect of oral supplementation of vitamin C on various semen parameters in oligospermic, infertile, otherwise healthy individuals. Various semen parameters, including sperm motility, sperm count, and sperm morphology, were studied before and after the vitamin C treatment. A total of 13 infertile patients were included. Their ages ranged between 25 and 35 years. They had no genital infection or varicocele. Physical examination and other routine laboratory investigations were normal. General semen analysis revealed oligozoospermia (mean sperm count was 14.3 +/- 7.38 x 10(6) sperms/mL, mean sperm with normal morphology was 43 +/- 7.87%, and mean sperm motility was 31.2 +/- 9.61%). Testicular biopsy was not done. These patients received in an open trial of 1,000 mg of vitamin C twice daily for a maximum of 2 months. Results showed that the mean sperm count was increased to 32.8 +/- 10.3 x 10(6) sperms/mL (P < .001) after 2 months of vitamin C intake. The mean sperm motility was increased significantly to 60.1 +/- 8.47% (P < .001), and mean sperms with normal morphology increased significantly to 66.7 +/- 4.77% (P < .001). This study showed that vitamin C supplementation in infertile men might improve sperm count, sperm motility, and sperm morphology and might have a place as an additional supplement to improve the semen quality towards conception.     

Semen quality and reproductive endocrine function in relation to biomarkers of lead, cadmium, zinc, and copper in men

Blood lead (BPb), activity of delta-aminolevulinic acid dehydratase (ALAD), erythrocyte protoporphyrin (EP), blood cadmium (BCd), serum zinc (SZn), seminal fluid zinc (SfZn), serum copper (SCu), and parameters of semen quality and of reproductive endocrine function were measured in 149 healthy male industrial workers 20-43 years of age. The group contained 98 subjects with slight to moderate occupational exposure to Pb and 51 reference subjects. All of the subjects lived in Zagreb, Croatia. Significant (p < 0.05) correlations of BPb, ALAD, and/or EP with reproductive parameters indicated a Pb-related decrease in sperm density, in counts of total, motile, and viable sperm, in the percentage and count of progressively motile sperm, in parameters of prostate secretory function (SfZn, acid phosphatase, and citric acid in seminal fluid), and an increase in abnormal sperm head morphology, serum testosterone, and estradiol. These associations were confirmed by results of multiple regression, which also showed significant (p < 0. 05) influence of BCd, SZn, SCu, smoking habits, alcohol consumption, or age on certain reproductive parameters. These effects were mainly of lower rank and intensity as compared to Pb-related reproductive effects, whereas BCd contributed to a decrease in sperm motility and an increase in abnormal sperm morphology and serum testosterone. No significant Pb- or Cd-related influence was found on levels of the lactate dehydrogenase isoenzyme LDH-C(4) and fructose in seminal fluid or on follicle-stimulating hormone, luteinizing hormone, and prolactin in serum. The seminal fluid concentrations of Pb (SfPb) and Cd (SfCd) were measured in 118 of the 149 subjects, and a highly significant (p < 0.0001) correlation was found between BPb and SfPb levels (r = 0.571) and between BCd and SfCd levels (r = 0.490). The overall study results indicate that even moderate exposures to Pb (BPb < 400 microg/L) and Cd (BCd < 10 microg/L) can significantly reduce human semen quality without conclusive evidence of impairment of male reproductive endocrine function.