Semen quality of 1346 healthy men, results from the Chongqing area of southwest China

106

Male reproductive disorders that are of interest from an environmental point of view include sexual dysfunction, infertility, cryptorchidism, hypospadias and testicular cancer. Several reports suggest declining sperm counts and increase of these reproductive disorders in some areas during some time periods past 50 years. Except for testicular cancer this evidence is circumstantial and needs cautious interpretation. However, the male germ line is one of the most sensitive tissues to the damaging effects of ionizing radiation, radiant heat and a number of known toxicants. So far occupational hazards are the best documented risk factors for impaired male reproductive function and include physical exposures (radiant heat, ionizing radiation, high frequency electromagnetic radiation), chemical exposures (some solvents as carbon disulfide and ethylene glycol ethers, some pesticides as dibromochloropropane, ethylendibromide and DDT/DDE, some heavy metals as inorganic lead and mercury) and work processes such as metal welding. Improved working conditions in affluent countries have dramatically decreased known hazardous workplace exposures, but millions of workers in less affluent countries are at risk from reproductive toxicants. New data show that environmental low-level exposure to biopersistent pollutants in the diet may pose a risk to people in all parts of the world. For other toxicants the evidence is only suggestive and further evaluation is needed before conclusions can be drawn. Whether compounds as phthalates, bisphenol A and boron that are present in a large number of industrial and consumer products entails a risk remains to be established. The same applies to psychosocial stressors and use of mobile phones. Finally, there are data indicating a particular vulnerability of the fetal testis to toxicants-for instance maternal tobacco smoking. Time has come where male reproductive toxicity should be addressed form entirely new angles including exposures very early in life.

Section: Introductionmentioning

confidence: 97%

Male reproductive organs are at risk from environmental hazards

Bonde¹

2009

106

“…Previous data from screened and general populations showed that there are obvious differences in semen quality between continents [6], countries [7] and even different areas in the same country [6,8,9]. Some of the studies also revealed temporal differences [10].…”

Section: Dear Editormentioning

confidence: 99%

“…Profound comments on this regard have been made and published in the Special Issue in Asian Journal of Andrology on "Semen analysis in 21st Century Medicine" in Issue 1 in 2010 [2][3][4][5]. In this letter, I would like to present some of my views and suggestions on reference limits of semen parameters.Previous data from screened and general populations showed that there are obvious differences in semen quality between continents [6], countries [7] and even different areas in the same country [6,8,9]. Some of the studies also revealed temporal differences [10].…”

mentioning

confidence: 99%

Reference limits: limited references in laboratories worldwide

Huang¹

2010

The newly revised World Health Organization (WHO) semen analysis manual provides the lower refe rence limits of semen parameters based on "the raw data from between about 400 and 1 900 semen samples, from recent fathers in eight countries on three continents": Australia, Europe and North America [1]. The other continents, Asia, Africa, and South America, and most regions of the above three continents, such as southern Europe, were not represented in the raw data used to generate the reference limits. To my knowledge, no valid and well-controlled data regarding semen from men whose partners had conceived within the preceding 12 months have been collected from these unrepresented regions. Profound comments on this regard have been made and published in the Special Issue in Asian Journal of Andrology on "Semen analysis in 21st Century Medicine" in Issue 1 in 2010 [2][3][4][5]. In this letter, I would like to present some of my views and suggestions on reference limits of semen parameters.Previous data from screened and general populations showed that there are obvious differences in semen quality between continents [6], countries [7] and even different areas in the same country [6,8,9]. Some of the studies also revealed temporal differences [10]. The underlying reasons were unclear. Temporal and geographical differences in semen quality might reflect differences in environmental factors and, ethnic or genetic backgrounds or a combination of factors. Although more studies are needed to understand the full biological significance of these differences, a study by Joffe et al. [11] suggested that they might be related to differences in fecundity. The observation that spermatogenesis in Asian men appears to be more susceptible to suppression by steroidal contraceptives than that in Caucasian men has been proposed to be related to ethnic differences in testicular structure (smaller testes, reduced number and function of Sertoli cells and reduced daily sperm production) and spermatogenic potential [12]. Differences in reproductive endocrinology between Asian men and Caucasian men have also been suggested [13]. It is possible that more sperm are produced in individuals in some ethnic populations, resulting in higher fecundity. Even in cases of similar levels of sperm production, it is possible that higher fecundity can be achieved by sperm that are better able to fertilise the egg or, conversely, by eggs that are easier to be fertilized. As a result, the fifth centiles (with 95% confidence intervals) from the raw data derived from a population with higher sperm production might be higher. These values would be lower in a population with sperm or eggs that result in higher fecundity. Therefore, it seems highly reasonable to suppose that the reference limits in men whose partners were pregnant within the last 12 months vary among countries with different ethnic backgrounds. Great caution should be taken when using the WHO manual's reference limits

“…16 In China, up to 63% of men have at least one semen parameter value lower than the WHO lower reference values (2010), with potential implications for fertility. [30][31][32][33] Other groups have also looked at sperm concentrations as a function of birth date, finding lower sperm concentrations in men born more recently. 34,35 Several recent studies have readdressed the question of whether there has been a secular trend towards a decline in sperm concentration.…”

Section: Can There Be a Consensus On Sperm Counts?mentioning

confidence: 99%

Counting your sperm before they fertilize: are sperm counts really declining?

Pastuszak

Lamb²

2013

A purported global decline in sperm counts has been a source of controversy since the early 1990s. Numerous studies performed since then, as well as reanalysis of the original data, show either no changes, or even increases, in sperm concentrations over time. In this review, we discuss the 1992 meta-analysis that initiated the continuing debate on whether sperm concentrations are declining, and the community discussion surrounding it over the past two decades. We also highlight studies evaluating sperm concentrations performed since the initial study that produced different results, and conclude that no definitive cause for a decrease in sperm counts has been established, and the effects of geography and environment on sperm counts are unclear.Approximately 15% of couples are considered infertile, with a male factor implicated in up to 50% of cases, underscoring the essential contribution of the male in conception. 1 However, only over the past two decades have we begun to understand the degree to which men contribute to a couple's infertility, which historically was attributed to the female partner. One quarter or more of infertile men have an unknown cause for their infertility, and while recent work suggests that many of these etiologies are genetic, we cannot exclude the impact of environmental factors on the male reproductive system, which have been incompletely defined.Work over recent decades has identified a potential decline in sperm concentrations, with at least one explanation being an increase or change in environmental pollutant levels. In 1992, a meta-analysis of sperm concentrations derived from 61 papers dating between 1938 and 1990 involving semen quality from 14 476 men found that both sperm concentrations and seminal volumes had dropped significantly during that period. 2 This was followed in 1993 by a manuscript suggesting that this decrease in sperm concentrations was partly due to environmental contamination with estrogenic compounds. However, there was little evidence identifying estrogens in the geographical areas where sperm concentrations appeared to be declining, or other evidence directly linking estrogenic pollution with declines in male fertility. 3 These works triggered a continuing discourse and numerous investigations to evaluate the verity of these claims. However, current data have failed to demonstrate a decrease in either sperm concentrations or male fertility.Owing to the large amount of unclear and confounding data, it is difficult to determine whether male fertility rates are truly declining. Fertility assessment in both men and women is made more difficult by the wide range of sperm concentrations that can result in pregnancy. Indeed, sperm count alone cannot define the fertility potential of a couple. Nevertheless, from the authors' viewpoint, the available data do not support a global decline in sperm concentrations or male fertility. We highlight the limitations of the original work claiming this decline, and show that current data, including data by the authors of the...