Health effects in fish of long-term exposure to effluents from wastewater treatment works

Abstract

Concern has been raised in recent years that exposure to wastewater treatment effluents containing estrogenic chemicals can disrupt the endocrine functioning of riverine fish and cause permanent alterations in the structure and function of the reproductive system. Reproductive disorders may not necessarily arise as a result of estrogenic effects alone, and there is a need for a better understanding of the relative importance of endocrine disruption in relation to other forms of toxicity. Here, the integrated health effects of long-term effluent exposure are reported (reproductive, endocrine, immune, genotoxic, nephrotoxic) . Early life-stage roach, Rutilus rutilus, were exposed for 300 days to treated wastewater effluent at concentrations of 0, 15.2, 34.8, and 78.7% (with dechlorinated tap water as diluent). Concentrations of treated effluents that induced feminization of male roach, measured as vitellogenin induction and histological alteration to gonads, also caused statistically significant alterations in kidney development (tubule diameter), modulated immune function (differential cell count, total number of thrombocytes), and caused genotoxic damage (micronucleus induction and single-strand breaks in gill and blood cells). Genotoxic and immunotoxic effects occurred at concentrations of wastewater effluent lower than those required to induce recognizable changes in the structure and function of the reproductive endocrine system. These findings emphasize the need for multiple biological end points in tests that assess the potential health effects of wastewater effluents. They also suggest that for some effluents, genotoxic and immune end points may be more sensitive than estrogenic (endocrine-mediated) end points as indicators of exposure in fish.

Figure 1

Histopathology of roach. (A) Undifferentiated gonad (G) of a 300-dph roach. The gonad consists of several primordial germ cells (PGC). Scale bar = 100 μm. (B) Ovary of a 300-dph female roach reared in tap water. The ovary contains oogonia (O) and primary oocytes (PO). The plate also shows the ovarian cavity (OC). Scale bar = 200 μm. (C) Testis of a 300-dph male roach reared in tap water. The testis contains spermatogonia A (SGA) and is connected to the mesentery (M) by a single point of attachment, the sperm duct (SD). Scale bar = 100 μm. (D) Gonad of a 300-dph intersex roach reared in 80% effluent. The testis contains spermatogonia A (SGA) and is connected to the mesentery (M) by two points of attachment (large arrows), forming a femalelike ovarian cavity (OC). Scale bar = 200 μm.

Figure 2

(A) Percentage of fish with male germ cells that had femalelike ovarian cavities (i.e., feminized males) in each treatment group. (B) Mean whole-body VTG concentrations (n = 30; mixed sex) for all treatment groups. Error bars are SEM. Significantly different from control: *p < 0.05, ^#p < 0.001.

Figure 3

(A) Olive tail moment (comet assay) in roach blood cells (n = 20 fish for all treatment groups). (B) Average number of Mn per 1,000 roach cells (n = 20 fish). (C) Average number of lymphocytes per 200 leukocytes in blood of roach (n = 20 fish). (D) Average number of thrombocytes per 200 leukocytes in blood of roach (n = 20 fish). Error bars represent 2× SE. Significantly different from control: *p < 0.001.

Figure 4

Histopathology of roach kidney. (A) Transverse section through the trunk kidney of a 300 dph roach reared in tap water. Kidney tubules (T) and a blood vessel (BV) are shown. Scale bar = 100 μm. (B) Transverse section through the trunk kidney of a 300-dph roach reared in 80% effluent. Several BCs and DNs were present at various stages of development, among mature tubules (T). Scale bar = 200 μm.

Figure 5

Kidney histopathology parameters. (A) Kidney tubule diameter of roach (± SE). (B) Number of BCs and DNs per trunk kidney section (± SE). Significantly different from control: *p < 0.05, #p < 0.001.

Figure 6

Lowest observed effect concentrations (LOEC) for different forms of developmental toxicity.