The effect of air dust pollution on semen quality and sperm parameters among infertile men in west of Iran

Abstract

Background: Pollutants during haze and Asian dust storms are transported out of the Asian continent, affecting the regional climate and the hydrological and biogeochemical cycles. Nonetheless, no specific studies evaluated the dust particles influence on semen quality in a specific geographical area.

Objective: In this article, we investigated the effect of dust particles on semen quality and sperm parameters among infertile men.

Methods: A descriptive-analytic study was conducted among 850 infertile men between 2011 and 2015 years. Semen quality was assessed according to the WHO 2010 guidelines, including sperm concentration, progressive motility, and morphology. Four-year average dust particle concentrations were estimated at each participant’s address using the Air Pollution Monitoring Station affiliated with the Department of Environment of Kermanshah city were gathered.

Results: Dust particle levels were highest in the summer months, in Kermanshah province. Our results show that, dust pollution was found to be significantly negatively correlated with sperm morphology and sperm concentration before and after lab-processing, but sperm progressive motility is low sensitive to dust particles.

Conclusions: Our findings showed that exposures to dust particle may influence sperm quantity in infertile men, consistent with the knowledge that sperm morphology and concentration are the most sensitive parameters of dust pollution.

Keywords:

• Male infertility
• dust particles levels
• air dust pollution
• Asian dust storms
• sperm quality

1. Introduction

The one key factor that determines male reproductive health is semen quality. In the past two decades, there has been a growing concern regarding the progressive decline in semen quality, in particular, for the sperm concentration and the sperm morphology and due to an increase in the infertility rate and azoospermia in men [1–3]. Although major reasons are not clear, to date, we have known loads of factors might have a negative influence on male sperm quality such as air pollutants, smoking, drinking, overweight, and obesity [4], advanced male age [5] late onset hypogonadism (LOH) [6] special diseases, social stress, polycyclic aromatic hydrocarbon (PAH) [7], heavy metal and particulate matter [8–10].

East Asian dust storms is assumed to be one in all the biggest and strongest sources of aerosols and trace gases on Earth. Giant amounts of aerosols and trace gases from the Asian continent may be transported to the Asian countries throughout winter and spring monsoons. Also the effects of Asian dust and haze particles area unit dependent upon the physical (e.g. particle size, number, and spatial distribution) of Asian aerosols in layer. The dust particles are mostly made out of clay (PM_0.01) and silica (PM₁₀), in this manner PM_2.5–10 (the typical meaning of the coarse portion embraced in air pollution monitoring observing and in epidemiological investigations) ought to be utilized with alert as a particular marker of dust pollution, which is likely better depicted by PM_0.01–10 [11]. During the recent years, a substantial amount of dust and dirt originating from Iraqi and Saudi deserts and arid wastelands has blanketed large areas of the Middle East, not least in Iran [12]. Ghasem [13] showed that, the westerly winning breeze conveyed a high volume of PM that expanded number of dust event days in Iran.

Kermanshah, a city in west of Iran [14], revealed that Kermanshah as genuinely vital city experienced air pollution specially dust storm amid the current decade and it is at the ninth rank among most populated urban pollution in Iran. Therefore, these findings suggested that PM_0.01–10, is one of the most important risk factors in our cities at present. Due to the small size of dust particles, they seem to be able to affect the transportation of high amount of pathogens [15]. Also, several studies have shown that exposure to air pollution has been linked to alterations in sperm parameters consequently increasing the risk of infertility in men [9,16–20]. These examinations have fundamentally focused on the impact of pollutants from gasoline, coal, and other fossil vitality sources; be that as it may, little attention has been paid to the consequences of dust and sand on semen quality and west of Iran that was affected by the Middle Eastern Dust (MED) storm was not an exception [21]. To the best of our insight, there were no already distributed information on the impact of the dust and sand deployed in the Middle East on semen quality and sperm parameters among infertile men. Thus, we tried to assess the theory that these pollutants can influence sperm parameters and decline semen quality.

2. Materials and methods

2.1. Study design and subject recruitment

A retrospective-analytical study was completed in the region of Kermanshah (is found 525 km 326 miles from Tehran) in the western piece of Iran. Kermanshah province, with total number of inhabitants as 1,890,000 people and a zone of 90 km², has the ninth rank among most populated regions in Iran. This examination was affirmed by the Ethics Committee of Kermanshah University of Medical Sciences. Indices of the health risk in ambient air of Kermanshah were assessed using Air Quality Health Impact Assessment Tool (AirQ). The information of PM_0.01–10 was taken from Kermanshah Environmental Protection Agency (KEPA) which was estimated by Beta attention procedure. The study population consisted of 850 infertile men undergoing a semen analysis from 1st February 2011 to 29th November 2015 at the Motazedi Infertility Center of Kermanshah, without any selection. All sperm samples were collected and analyzed in a single laboratory. To maintain confidentiality, all information was kept confidential by the research team. A computing database was created, registering sperm analyses performed for each enrolled patient. Moreover, the city of residence, the date of birth, age, the date of examination, infertility type (primary or secondary), and semen analysis were registered for each man. The inclusion criteria had the following characteristics: males, age 20–60 and permanent residents of the Kermanshah area.

2.2. Semen collection and the analyses

All participants were asked to be abstinent for 2–7 days before contributing a semen analysis. We assessed traditional semen parameters for the first crude examples, including appearance, viscosity, liquefaction time, pH value, semen volume, sperm concentration, and motion parameters, using WHO (2010) manual. The samples were set at 37 °C promptly after collection and sperm parameters were evaluated within one hour from semen collection. The volume was estimated by aspiration into a 10 ml pipette giving 0.1 ml precision. The pH value was measured by pH tape (pH 6.5–10.0) and recorded after 30 s.

For the appraisal of sperm motility, 10 µl of very much blended semen was put on one clean glass slide secured by a coverslip utilizing positive phase-contrast microscopy at a magnification of ×400. The preparation was put on the warming phase of a microscope and instantly analyzed at total magnification of ×20. The microscope field was checked methodically and the sperm were classified in the four motility classifications: quick progressive sperm (rapid progressive), moderate progressive sperm, non-progressive sperm, and immotile sperm. For the evaluation of sperm concentration, every semen sample was completely blended. An aliquot of the example was weakened (1:20) with formaldehyde and again altogether blended. The sperm concentration was assessed by using a Neubauer hemocytometer (Wertheim, Germany), and six unique parts were checked at a total microscope magnification of ×400. Just sperm with tails were checked. We used the “feathering” technique [22,23], to perform the analysis for sperm morphology assessment. In brief, the air-dried spread was fixed in 96% ethanol and then Papanicolaou staining were prepared by mixing a droplet of semen and a droplet of stain (approximately 15 µl of each) on a warm slide and spreading the sample with a wood applicator after quickly mixing it. The slide was immediately placed on a slide warmer at 37 °C and gently blown over in order to quickly dry the sample. Two slides were utilized for each fresh semen sample. The criteria of the characterizations including “head shape//size defects”, “neck and midpiece abandons”, “tail imperfections” and “cytoplasmic beads” was done according the WHO manual (2010).

2.3. Air pollution data and exposure assessment

Air pollution information was acquired from the Kermanshah Environmental Protection Agency (KEPA). The day by day average concentrations of PM_0.01–10 were estimated by Beta constriction strategy at two air quality checking stations in Kermanshah, between 2011 and 2015. The information of the stations preprocessed in Excel using large scale (VBA) programing to change over the information into format of AirQ. As indicated by the specialized rules of the worldwide guidelines, the area of these observing stations must be sufficiently separate from some other emanating sources, e.g. coal, waste, or oil-consuming boilers; heaters, and incinerators. Monthly air pollution data average concentrations and trends of PM₁₀ in the ambient air of Kermanshah, Iran, during 2011–2015 are presented in Figure 1. In order to reduce the variation of sperm, each sample was checked by two well-trained technicians for semen quality, with one professional technician appearance, viscosity, liquefaction time, pH value, and semen volume, and the other estimating sperm concentration, progressive motility, and morphology.

Figure 1. Monthly air pollution data. The panel shows the monthly average concentrations and trends of PM 10 in the ambient air of Kermanshah, Iran, during 2011–2015.

2.4. Statistical analysis

Since semen parameters follow markedly skewed (non-normal) distributions, the percentiles, medians, and means were calculated. The information was additionally condensed utilizing mean (±SD), 25th, 50th, and 75th percentiles (Table 2), and were stratified by age (Table 3). The Kruskal–Wallis analysis of variance, a nonparametric test, was utilized to look at medians between groups. We utilized a linear regression model to look at the independent effects of dust particles on semen parameters (Table 4). All semen parameters were log-transformed (base 10) to improve the normality as dependent variables in the linear models. At last, to distinguish the relationship between dust particles and sperm parameters (before and after lab processing), Spearman's connection coefficients and essential component analysis were performed by using SPSS variant 13.0, SPSS, Chicago (Table 5). This coefficient is frequently used when Pearson's connection coefficient is not legitimate because of information being plainly non-normal, or where information is provided in the form of ranks rather than in the form of measurements. The tests were two-sided, and the level of significance was set up at 0.05.

Table 1. Demographic characteristics of the study populations.

Characteristics	n (%)
Age (years)
20–30	219 (25.8)
31–40	463 (54.5)
41–50	150 (17.6)
51–60	13 (1.5)
>60	5 (0.6)
Residential location
Large cities	391 (46)
Small cities	459 (54)
Educational level
High school diploma or lower	625 (73.5)
Bachelor of science or Master of science	214 (25.1)
Doctorate or higher	11 (1.4)
Occupation
Proletarian	101 (11.9)
Solder	101 (11.9)
Clerk	337 (39.7)
Driver	53 (6.2)
Other	460 (54.1)

Data are presented as the number (percentage) for categorical variables.

Table 2. Descriptive statistics for semen parameters before and after laboratory processing of 850 infertile men who presented at Motazedi Infertility Center, 2011–2016.

Sperm parameters	n	Before processing				After processing				Percentage lower than WHO criteria
		Mean (±SD)	25th	50th	75th	Mean (±SD)	25th	50th	75th
Sperm PH value	850	7.53 (±0.07)	7.2	7.5	7.8	7.53 (±0.07)	7.2	7.5	7.8	77.0
Sperm volume (ml)	850	3.26 (±1.87)	2	3	4.5	3.26 (±1.87)	2	3	4.5	92.5
Sperm concentration (10^6/ml)	849	41.77 (±24.45)	25	40	55	36.06 (±22.13)	20	35	50	78.2
Sperm progressive motility (%)	849	21.65 (±10.16)	15	20	30	87.17 (±23.70)	90	98	99	60.7
Sperm morphology (%)	849	5.89 (±2.84)	4	35	8	13.06 (±9.05)	6	10	20	12.4

Abnormal values of semen parameters were defined by the World Health Organization (WHO, 1999 and 2010) standards: pH value <7.2, semen volume <2 ml, sperm concentration <20 × 10⁶/ml, sperm total count <40 × 10⁶ and sperm motility <50%.

Table 3. Summary of semen parameters according to different age groups.

Semen parameters	Age
	20–30	31–40	41–50	51–60	Total	p-Value^a
Sperm concentration before processing (10^6/ml)	(43.72 ± 26.73)	(40.51 ± 22.73)	(43.37 ± 26.07)	(39.84 ± 17.54)	(41.84 ± 24.49)	0.40
Sperm motility before processing (%)	(21.05 ± 11.29)	(22.17 ± 9.17)	(21.40 ± 9.60)	(19.22 ± 17.54)	(21.69 ± 10.17)	0.59
Sperm morphology before processing (%)	(5.70 ± 3.08)	(5.93 ± 2.73)	(6.03 ± 2.77)	(6. 23 ± 3.37)	(5.9 ± 2.84)	0.01
Sperm concentration after processing (10^6/ml)	(35.16 ± 22.13)	(35.95 ± 22.03)	(38.00 ± 22.48)	(37.38 ± 23.28)	(36.13 ± 22.14)	0.40
Sperm motility after processing (%)	(84.05 ± 27.18)	(88.05 ± 21.95)	(88.24 ± 22.95)	(86.38 ± 27.15)	(87.24 ± 23.66)	0.22
Sperm morphology after processing (%)	(12.25 ± 8.76)	(13.04 ± 8.73)	(14.49 ± 10.20)	(12.15 ± 7.83)	(13.08 ± 9.05)	0.87

^a Kruskal–Wallis analysis of variance was used to compare the median between groups.

Table 4. Correlation between semen parameters and PM_0.01–10 levels before and after lab processing.

Semen parameter	PM10 (µg/m^3) Before processing		After processing
	Standardized coefficient β	p-Value	Standardized coefficient β	p-Value
Sperm concentration (10^6 /ml)	−0.105*	0.002	−0.076*	0.023
Sperm motility (%)	−0.054	0.118	−0.020	0.557
Sperm morphology (%)	−0.126**	0.000	−0.146**	0.000

β, The Standardized coefficient Beta.

*Statistically significant at the level 0.05.

**Statistically significant at the level 0.01.

Table 5. Spearman’s Rho, correlation coefficients (R) with 99% confidence intervals between continuous variables in this study.

PM10 (µg/m^3 )			Semen parameters
			Before processing			After processing
			Sperm concentration (10^6 /ml)	Sperm motility (%)	Sperm morphology (%)	Sperm concentration (10^6 /ml)	Sperm motility (%)	Sperm morphology (%)
Spring	April	R	0.032	−0.002	−0.023	0.030	−0.019	−0.009
		p-Value	0.352	0.953	0.501	0.377	0.588	0.799
	May	R	0.068*	0.16	0.010	0.066	−0.003	0.015
		p-Value	0.048	0.636	0.771	0.055	0.921	0.652
	Jun	R	0.056	0.025	0.042	0.092**	0.012	0.010
		p-Value	0.103	0.469	0.220	0.008	0.726	0.762
Summer	July	R	0.055	0.039	0.011	0.064	0.002	0.010
		p-Value	0.090	0.259	0.758	0.065	0.953	0.762
	August	R	−0.934**	−0.641**	−0.539**	−0.793**	−0.322**	−0.4154**
		p-Value	0.000	0.000	0.000	0.000	0.000	0.000
	September	R	0.052	0.025	0.009	0.069*	0.013	0.019
		p-Value	0.129	0.470	0.796	0.045	0.704	0.574
Autumn	October	R	0.001	0.018	−0.106**	−0.039	−0.062	−0.190**
		p-Value	0.980	0. 593	0.002	0.254	0.076	0.000
	Number	R	0.006	−0.017	0.067*	0.008	0.074*	0.130**
		p-Value	0.872	0.623	0.050	0.825	0.030	0.000
	December	R	0.004	0.028	−0.058	−0.009	0.022	0.130**
		p-Value	0.904	0.420	0.089	0.795	0.514	0.000
Winter	January	R	0.058	0.019	0.050	0.065	−0.023	0.034
		p-Value	0.091	0.577	0.148	0.060	0.496	0.324
	February	R	0.001	0.016	−0.107**	−0.037	−0.060	−0.190**
		p-Value	0.973	0.643	0.002	0.282	0.079	0.000
	March	R	0.053	0.020	0.037	0.089**	0.011	−0.190**
		p-Value	0.124	0.556	0.276	0.010	0.743	0.002

R: Correlation coefficients.

*Correlation significant at the 0.05 level (two-tailed).

**Correlation significant at the 0.01 level (two-tailed).

3. Results

3.1. Subject characteristics

The general demographic characteristics of the 850 infertility men amid 2011–2015 years are condensed and presented in Table 1. In this investigation, the greater part of the aggregate subjects (54.5%) were 30–40 years of age. Roughly 50% of the sample subjects were living in neighboring little urban areas (54%). Most of the study subjects had high school education (73.5%) and working as a clerk (39.7%) (Table 1).

3.2. Semen parameters

The descriptive semen analysis parameters (before and after lab processing) among 850 infertile men are described in Table 2. As introduced in the table, the semen volume and total concentration were inside the high-normal values (92.5 and 78.2%, individually, as per the 2010 WHO criteria). The value of pH range was between 7.2 and 7.8 with a mean value of 7.53. A large proportion of the study samples had semen parameter values below the lower threshold of the WHO criteria, especially for progressive motility and sperm morphology (Table 2). Also, just 50.7% of the semen samples had normal semen parameters as indicated by the WHO 2010 criteria.

The summary of semen parameters according to different age groups is given in Table 3. There were no significant differences between different age groups for sperm concentration and sperm progressive motility (before and after lab processing) and normal morphology (after lab processing). But in the 20–30 and 51–60 years of age group, normal morphology (before lab processing) was significantly lower and higher than respectively in the other age group (Table 3).

3.3. Correlation of air pollution and semen quality

Table 4 shows adjusted regression coefficients and p-values for risk factor (PM_0.01–10) in connection to semen parameters. The sperm morphology (before and after lab processing) was significantly connected with the season. The outside presentation concentration for PM_0.01–10 was observed to be significantly and adversely connected with sperm concentration and morphology (before and after lab processing) (Table 4), but, no noteworthy affiliation was seen between PM_0.01–10 and sperm progressive motility.

Spearman’s rho, relationship coefficients (R) with 99% confidence intervals between continuous variables in this investigation are given in Table 5. PM_0.01–10 Hazardous levels were highest in the August month (Figure 1), when the ambient temperature was the highest. PM_0.01–10 level correlated negatively with current sperm concentration, sperm motility, and sperm morphology (Table 5). No correlation was found between PM_0.01–10 (µg/m³) levels in spring and winter months and current sperm motility or concentration.

4. Discussion

Kermanshah is at 6th place among the most polluted cities in view of annual average of dust events and PM_0.01–10 in the world [24]. Uneven geography, warm climate amid summer time and additionally frequency of dust storms gave confounded conditions to take gauge to experience urban air pollution obstacle in Kermanshah. On the other hand, particulate matter particularly dust particles are Kermanshah’s most problematic pollutant in terms of harm to human health. Recent epidemiologic studies have shown that dust pollutions coincide with increases in daily admissions and clinic visits for allergy diseases [25,26], such as asthma [27,28], allergic rhinitis [29], conjunctivitis [30], induces lung inflammation [31], and splenocytes [32] and deterioration in children with mild asthma [26].

But no studies on the effect of dust pollutions on semen quality and sperm parameters among infertile men have been published so far. Based on our extensive search on most reputable scientific sites, this is the biggest examination researching the health effects of dust particle as an air pollutant in a specific era on semen quality of infertile men and to report that the dust is the first occasions influence on quality-related semen parameters in the area of Kermanshah, Iran.

Dust particles are one of the main pollutants that affect air quality in Kermanshah province. It is a complex mixture of solid and liquid particles that remain suspended in the air, and vary in size and composition. In our study, the concentration of dust particles presented a fluctuation in different seasons with a peak in summer (particularly in August month) in Kermanshah province during 2011–2015 years (Figure 1), our result is strongly similar to the study of Marzouni et al. [14]. The results of our study suggest that the dust deployed in the Middle East, similar to other pollutants, can affect quality-related semen parameters. This finding is in line with previous studies, most of which have observed significant associations between air pollution and sperm concentration [8,33]. Also, exposure to environmental agents such as dust and air pollutants has shown to induce changes in DNA damage and methylation. Over the past decade, several human studies have focused on correlation between epigenetic processes, such as DNA damage and gene‐specific methylation and air pollution exposure, showing positive correlation between dust levels, sperm DNA damage, such as sperm DNA strand breaks with air pollutant exposure [34–37]. Thus, these results suggested that the dust pollution might have adverse effects on semen quality, the fertilization ability of sperm, and the function. For this reason, identification of sperm DNA damage would help to understand the causes of male infertility, however, the exact mechanisms of different injury from exposure to air pollutants are not yet fully understood.

Even the results show certain reliable and clear information, this study was an exploratory research, and there were many limitations. First, a cause-effect relationship cannot be sustained with simple correlations. Second, the effect on sperm motility was minimal and is unlikely to affect the fertility of the population studied. Third, most participants (97%) had only one progressive motility measurement and this limited us to perform a rapid progressive motility and total motility-measures analysis, which would address within-person variations over time. Finally, our study also lacked data on other gaseous air pollutants and future studies need to take it into consideration. So, further studies are warranted to investigate the underlying mechanism between dust pollution and semen’s parameters.

5. Conclusions

In a nutshell, results from the present study revealed a robust association between exposure to dust particles pollution and low percentage of sperm morphology and sperm concentration in infertile men. Although there are no prospective trials that would allow us to draw a conclusion about causality, but rather just evidence from observational studies. Our study represents the first attempt to evaluate a possible relationship between dust particles pollution and semen parameters (before and after laboratory processing) in a defined and well-characterized geographic area. These results suggest that environmental dust particle may influence sperm quantity, consistent with the knowledge that sperm morphology and concentration are the most sensitive parameters of dust pollution but, sperm progressive motility, seem to be less informative. Thus, further studies are warranted to confirm these findings and its underlying mechanism. Also, it should be noted that for diminishing the health impacts, the policy makers should focus on measures which decrease the amount of dust particles in ambient air.

Acknowledgments

The authors are grateful to the Department of Environment (DOE) at Kermanshah province and the staff at Motazedi Infertility Center for cooperating with us in the current study.

Disclosure statement

No potential conflict of interest was reported by the authors.