In vivo exposure to electronic waste (e-waste) leachate and hydraulic fracturing fluid adversely impacts the male reproductive system

Abstract

Human health effects can arise from unregulated manual disassembly of electronic waste (e-waste) and/or hydraulic fracturing fluid spills. There is limited literature on the effects of e-waste and hydraulic fracturing wastewater exposure on the male reproductive system. Thus, this proof-of-concept study begins to address the question of how wastewater from two potentially hazardous environmental processes could affect sperm quality. Therefore, three groups of eight-week-old adult mice were exposed (5 d/wk for 6 wks) via a mealworm (Tenebrio molitor and Zophabas morio) feeding route to either: (1) e-waste leachate (50% dilution) from the Alaba Market (Lagos, Nigeria); (2) West Virginia hydraulic fracturing flowback (HFF) fluid (50% dilution); or, (3) deionized water (control). At 24-hours (hr), 3 weeks (wk), or 9-wk following the 6-wk exposure period, cohorts of mice were necropsied and adverse effects/persistence on the male reproductive system were examined. Ingestion of e-waste leachate or HFF fluid decreased number and concentration of sperm and increased both chromatin damage and numbers of morphological abnormalities in the sperm when compared to control mice. Levels of serum testosterone were reduced post-exposure (3- and 9-wk) in mice exposed to e-waste leachate and HFF when compared to time-matched controls, indicating the long-term persistence of adverse effects, well after the end of exposure. These data suggest that men living around or working in vicinity of either e-waste or hydraulic fracturing could face harmful effects to their reproductive health. From both a human health and economic standpoint, development of prevention and intervention strategies that are culturally relevant and economically sensitive are critically needed to reduce exposure to e-waste and HFF-associated toxic contaminants.

Keywords: Electronic waste; Hydraulic fracturing; Hydrofracturing, male reproductive health.

Figure 1.

Experimental design. Three exposure groups were exposed to either: e-waste leachate (n=15); HFF (n=15); or deionized water controls (n=15). Necropsy and tissue collection were performed at three post-exposure timepoints (24-hr, 3-wk, and 9-wk). The right cauda epididymis was used to collect sperm for determining sperm quality (i.e., sperm count, density, viability, morphology, maturity and chromatin integrity). Blood was collected at the time of necropsy for differential blood counts, and serum recovered for assessing circulating testosterone levels (Figure created with BioRender.com)

Figure 2.

Mean of (a) Mean sperm count (x 106) (b) percent sperm viability (% of control) and (c) sperm density in mice exposed by ingestion of injected mealworms with de-ionized water (control), e-waste leachate and HFF fluid exposed at 24-hr, 3-wk and 9-wk post a 6-wk exposure. Data are means ± standard error (SE) for the control, e-waste leachate, and HFF fluid groups, respectively. SE is shown with error bars. Significantly different groups at p<0.05 compared to control at each timepoint are indicated by *.

Figure 3.

Examples of normal sperm and morphological abnormalities in mice exposed by ingestion of injected mealworms for 6-wk to e-waste leachate or HFF fluids. (a) Normal mouse sperm, (b) Misfolded tail, (c) Detached head, (d) Missing tail, (e) Cytoplasmic droplet, (f) Broken tail, and (g) Amorphous head. Coomaassie blue stained images observed by light microscopy using oil immersion (100X magnification)

Figure 4.

Mean of sperm: (a) total, (b); head, (c); tail and (d); midpiece abnormalities (per 200 sperm) in mice exposed by ingestion of injected mealworms with either deionized water (control), e-waste leachate or HFF fluid at 24-hr, 3-wk and 9-wk post-exposure timepoints. Data are shown as means ± standard error (SE) for control, e-waste leachate, and HFF fluid groups, respectively. *Significantly different p<0.05 compared to controls at each timepoint.

Figure 5.

(a) Sperm chromatin damage (no. of sperm with damage/200 sperm) and (b) sperm maturity (no. of sperm with residual histones/200 sperm) in mice exposed by ingestion of mealworms injected with deionized water (control), e-waste leachate or HFF fluid and examined 24-hr, 3-wk and 9-wk post-exposure. Data are shown as means ± standard error for the control, e-waste leachate, and HFF fluid groups, respectively. *Significantly different at p<0.05 compared to controls at each timepoint.

Figure 6.

(a) Total testosterone level (ng/ml); (b) temporal variation of testosterone level (ng/ml) in mice exposed by ingestion of wastewater fluid-injected mealworms with deionized water (control), e-waste leachate and HFF fluid exposed for and examined at 24-hr, 3-wk and 9-wk post-exposure. Data are shown as mean ± standard errors (n = 13–15) mice per each treatment group. *Significantly different (p<0.05) at each timepoint compared to controls.

Figure 7.

Circulating (a) neutrophil percentage; and (b) lymphocyte percentage in mice exposed by ingestion of injected mealworms with de-ionized water (control), e-waste and HFF fluid and examined 24-hr, 3-wk and 9-wk post-exposure. Data are shown as means ± standard error (SE). *Significantly different at p<0.05 for each timepoint compared to controls.