Microplastic presence in dog and human testis and its potential association with sperm count and weights of testis and epididymis

Abstract

The ubiquitous existence of microplastics and nanoplastics raises concerns about their potential impact on the human reproductive system. Limited data exists on microplastics within the human reproductive system and their potential consequences on sperm quality. Our objectives were to quantify and characterize the prevalence and composition of microplastics within both canine and human testes and investigate potential associations with the sperm count, and weights of testis and epididymis. Using advanced sensitive pyrolysis-gas chromatography/mass spectrometry, we quantified 12 types of microplastics within 47 canine and 23 human testes. Data on reproductive organ weights, and sperm count in dogs were collected. Statistical analyses, including descriptive analysis, correlational analysis, and multivariate linear regression analyses were applied to investigate the association of microplastics with reproductive functions. Our study revealed the presence of microplastics in all canine and human testes, with significant inter-individual variability. Mean total microplastic levels were 122.63 µg/g in dogs and 328.44 µg/g in humans. Both humans and canines exhibit relatively similar proportions of the major polymer types, with PE being dominant. Furthermore, a negative correlation between specific polymers such as PVC and PET and the normalized weight of the testis was observed. These findings highlight the pervasive presence of microplastics in the male reproductive system in both canine and human testes, with potential consequences on male fertility.

Keywords: male reproductive; particulates; polymers; pyrolysis GC/MS; sperm count; testis.

Figure 1.

Quantitative analysis of microplastic contamination, distribution, and composition in canine testicular tissues. A circular bar chart displays the concentration of 12 types of microplastics in 47 dog testis samples (A) and the percentage composition of each dog testis (B), the abundance of specific polymers (C), and a statistical summary (D). Each segment represents a unique sample and the length of each bar indicates the quantity of individual microplastics measured. The color coding corresponds to the type of microplastic, as per the legend on the right. Each cluster (A, B, C) corresponds with age groups 2–10, 11–36, and >36 months, respectively. Data were transformed using log₁₀(X + 1), and statistical comparison among the 12 types of polymers was conducted using 1-way ANOVA with post-hoc Tukey-Kramer HSD. Levels not connected by the same letter are significantly different at p ≤ .05.

Figure 2.

Quantitative analysis of microplastic concentration, distribution, and composition in human testicular tissues. The individual levels of 12 different types of microplastics were quantified in 23 human testicular tissue samples using Py-GC/MS analysis (A), the percentage composition of each testis (B), the abundance of specific polymers (C), and a statistical summary (D). Each radial segment represents a unique human sample ID, with the length of the bar indicating the level of a specific type of microplastic. Data were transformed using log₁₀(X + 1) for normalization and statistical comparison among the 12 types of polymers was conducted using 1-way ANOVA with post-hoc Tukey-Kramer HSD. Levels not connected by the same letter are significantly different at p ≤ .05.

Figure 3.

Comparative analysis of microplastic concentration and composition in canine and human testicular tissues. The box-and-whisker plot juxtaposed with a violin plot compares the sum of microplastic concentrations log-transformed with log₁₀(X + 1) in canine and human testicular tissues (A). Panel (B) shows the 2 donut charts illustrating the relative composition of different microplastic types in the testicular tissues of dogs (left) and humans (right). Each section of the donut charts represents a specific type of microplastic, with the percentage indicating its proportion relative to the total microplastic content found in the tissues. Statistical comparison was conducted using 1-way ANOVA. Levels not connected by the same letter are significantly different at p ≤ .05.

Figure 4.

Correlation analysis of microplastic concentration with body weight-corrected testis and epididymis weights, and sperm counts. This figure shows correlations between the log₁₀(X + 1)-transformed concentrations of various microplastics and body weight-normalized reproductive parameters in dogs. These parameters include testis weight (g/kg body weight), epididymis weight (g/kg body weight), and sperm count (number of sperm per g cauda epididymis/ml). Each parameter is assessed against the concentration of different types of microplastics, which are distinguished by unique colors. An asterisk (*) indicates a statistically significant correlation r coefficient at p ≤ .05.