Elsevier

Environment International

Volume 54, April 2013, Pages 134-140
Environment International

Baseline blood trihalomethanes, semen parameters and serum total testosterone: A cross-sectional study in China

https://doi.org/10.1016/j.envint.2013.01.016Get rights and content

Abstract

Toxicological studies showed that trihalomethanes (THMs), the most abundant classes of disinfection by-products (DBPs) in drinking water, impaired male reproductive health, but epidemiological evidence is limited and inconsistent. This study aimed to examine the associations of baseline blood THMs with semen parameters and serum total testosterone in a Chinese population. We recruited 401 men seeking semen examination from the Reproductive Center of Tongji Hospital in Wuhan, China between April 2011 and May 2012. Baseline blood concentrations of THMs, including chloroform (TCM), bromodichloromethane (BDCM), dibromochloromethane (DBCM), and bromoform (TBM) were measured using SPME-GC/ECD method. Semen quality and serum total testosterone were analyzed. Multivariable linear regressions were used to assess the associations of baseline blood THM concentrations with semen parameters and serum total testosterone levels. We found that baseline blood THM concentrations were not associated with decrements in sperm motility, sperm straight-line and curvilinear velocity. However, moderate levels of BDCM (β =  0.13 million; 95% CI: − 0.22, − 0.03) and DBCM (β =  4.74%; 95% CI: − 8.07, − 1.42) were associated with decreased sperm count and declined sperm linearity compared with low levels, respectively. Suggestive dose–response relationships were also observed between elevated blood TCM or ∑ THMs (sum of TCM, BDCM, DBCM and TBM) concentration and decreased sperm concentration (both p for trend = 0.07), and between elevated blood DBCM concentration and decreased serum total testosterone (p for trend = 0.07). Our results indicate that elevated THM exposure may lead to decreased sperm concentration and serum total testosterone. However, the effects of THM exposure on male reproductive health still warrant further studies in humans.

Highlights

► We performed the first study on the effects of baseline blood THMs on human male reproductive health. ► Moderate levels of BDCM and DBCM resulted in declined sperm count and linearity, respectively. ► Elevated blood TCM or ∑ THM concentrations might result in decreased sperm concentration. ► Elevated blood DBCM concentrations might lead to decreased serum total testosterone.

Introduction

Chlorination of drinking water in public water supplies successfully reduces the risk of water-borne infection disease. However, harmful disinfection by-products (DBPs) form when chlorine reacts with natural organic and inorganic compounds during preparation of drinking water. To date, more than 600 kinds of DBPs with different physicochemical and toxic properties have been identified (Richardson et al., 2007). The most abundant classes of DBPs are trihalomethanes (THMs), including chloroform (TCM), bromodichloromethane (BDCM), dibromochloromethane (DBCM), and bromoform (TBM). Humans are exposed to THMs through ingestion, inhalation and dermal absorption during their routine water-use activities such as water consumption, bathing, showering, and swimming in a lifelong time (Nieuwenhuijsen et al., 2009). Potential adverse health effects of THMs have been public health concerns worldwide.

Previously, some epidemiological studies have focused on an association between THM exposure and increased risk of cancer such as bladder and colon cancer (Cantor et al., 1998, Villanueva et al., 2004, Young et al., 1987). Epidemiological studies have also suggested associations between THM exposure and adverse reproductive outcomes such as low birth weight, spontaneous abortion, and birth defects (Toledano et al., 2005, Waller et al., 1998, Yang et al., 2007). The evidence for the relationship between THM exposure and male reproductive health in humans is limited, although toxicological studies showed that THMs, especially the brominated THMs, had the capacity to impair male reproductive health. Klinefelter et al. (1995) reported that exposure to BDCM in drinking water reduced sperm motility as assessed by significantly decreased mean sperm straight-line, average path, and curvilinear velocities. Potter et al. (1996) found that exposure to all four individual THMs produced a decrease in serum testosterone concentrations.

To our knowledge, there are only two epidemiological studies which have explored the relationship between THM exposure and semen quality (Fenster et al., 2003, Luben et al., 2007). However, the results from the two studies were inconsistent. In these studies, THM exposures were assessed by using THM concentrations in distribution systems as exposure surrogates, which may result in exposure misclassification because of temporal and spatial variability and various exposure routes for THMs (Parvez et al., 2011, Wei et al., 2010). Exposure biomarkers provide an alternative measurement to improve exposure assessment in epidemiological studies. Two biomarkers have been used to assess internal dose levels of THM exposure, including THMs in whole blood and expired air (Aggazzotti et al., 1998, Blount et al., 2006). Morning blood samples collected prior to any major water-use activity can be expected to yield baseline THM exposures (Weisel and Jo, 1996). Although breath samples are less invasive and result in better subject participation, blood levels are generally more sensitive to low exposure and represent an integrative measure of exposures from various routes (Miles et al., 2002).

We conducted a cross-sectional study in Wuhan, China, to examine the relationships between THM exposure, semen parameters and serum total testosterone. In this study, we measured THM concentrations in morning whole blood to assess internal doses of baseline THM exposure. To our best knowledge, our study is the first one using whole blood THMs as an exposure biomarker to evaluate the effects of THM exposure on male reproductive health in humans.

Section snippets

Study participants and data collection

We recruited study participants from men who presented to the Reproductive Center of Tongjing Hospital in Wuhan, China, to seek semen examination. During April 2011 to May 2012, a total of 467 men agreed to participate in the study and provided blood samples for analysis regardless of their prior knowledge of fertility status. We excluded 30 azoospermic men because the mechanism responsible for azoospermia may be related to an obstructive mechanism or Y-chromosome deletions. The study was

Characteristics of the study participants

The distribution of characteristics among the study population is shown in Table 1. Study participants were primarily Han (97.3%), with a mean age of 30.5 (± 5.8) years and BMI of 23.4 (± 3.8) kg/m2. There were 122 men (30.4%) who reported their abstinence time as more than six days. Among the all study participants, 295 men (73.7%) reported their total boiled tap water consumption as less than 1000 mL per day, 145 men (36.2%) reported their showering time as less than 10 min per day. However, only

Discussion

Our results showed that baseline blood THM concentrations were not associated with decrements in sperm motility, sperm VSL and VCL. However, we found that moderate levels of BDCM and DBCM were associated with decreased sperm count and sperm LIN compared with low levels respectively. We also observed suggestive dose–response relationships of elevated blood TCM and ∑ THM concentration with decreased sperm concentration. In two previous studies of THM exposure (using THMs in distribution systems

Conclusions

Our study found no evidence for the relationships between elevated blood THM concentrations and decreased sperm motility, sperm VSL or VCL. However, we found that moderate levels of BDCM and DBCM were associated with decreased sperm count and declined sperm LIN compared with low levels, respectively. We also observed a suggestive dose–response relationship of elevated blood TCM and ∑ THM concentration with decreased sperm concentration, and elevated blood DBCM concentration with decreased serum

Acknowledgments

We sincerely thank all participants for providing blood and semen samples in this study, as well as the others who gave their technical assistance. This study was supported by the National Natural Science Foundation of China (No. 81072264) and the National Key Technologies R&D Program of China (No. 2006BAI19B02).

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