4-nonylphenol (4-NP), a major degradation product of Nonylphenol ethoxylates (NPEos), is widespread in environment. In this study, the effects of long-term 4-NP exposure in drinking water on Japanese quails (Coturnix japonica) were investigated. A total of 45 quails were evenly divided into 15 groups and administrated with various doses (0.1 mu g L-1,1.0 mu g L-1, 10 mu g L-1 and 100 mu g L-1, which reflected the environmental concentrations of 4-NP) of 4-NP in drinking water. The results showed that 4-NP in drinking water had no effect on quails' food intake, but significantly decreased the quails' body weights (P < 0.05) in a time- and dose-dependent manner. The egg fertilization rates were also significantly decreased (P < 0.05) in all treatment groups. Moreover, the hatchability was significantly reduced (P < 0.05) in 10 mu g L-1 and 100 mu g L-1 groups, and the 14 d survival rates of young quails were significantly decreased (P < 0.05) in 1.0 mu g L-1,10 mu g L-1 and 100 mu g L-1 groups. Damaged spermatogenesis in male quails was observed in all treatment groups. Therefore, administration of 4-NP in drinking water impaired the reproductive ability of Japanese quails, and led to pathological lesions in the male gonads. (C) 2017 Elsevier Ltd. All rights reserved.