Effect of Chronic Noise Stress on Physiological Parameters and Antioxidant Status in Laboratory Rats

Urban noise pollution is an emerging environmental health concern in rapidly growing Nigerian cities, where proximity of residential and livestock holding areas to busy commercial centres, generators, and construction sites creates chronic acoustic stressors for both humans and animals. Noise stress activates neuroendocrine stress pathways, generates reactive oxygen species, and impairs immune function in laboratory and domestic species. This study investigated the effects of chronic noise exposure at 90 and 110 decibels on physiological parameters and antioxidant status in Wistar rats over four weeks, with reference to urban acoustic conditions in Aba, Abia State, South East Nigeria. Sixty rats were distributed into three groups: quiet control maintained below 40 decibels, 90 decibel noise exposure for four hours daily, and 110 decibel noise exposure for four hours daily. At the end of the exposure period, body weight, food intake, heart rate, blood pressure, and adrenal gland weight were measured. Serum cortisol, adrenaline, superoxide dismutase, catalase, glutathione peroxidase, and malondialdehyde were quantified. Rats exposed to 110 decibel noise showed significantly elevated serum cortisol, adrenaline, and blood pressure compared with controls. Adrenal glands were significantly heavier in both noise-exposed groups. Antioxidant enzyme activities were significantly reduced at 110 decibels, while malondialdehyde was markedly elevated. Body weight gain was significantly impaired in noise-exposed groups. These findings provide experimental evidence supporting the physiological stress burden of chronic noise on animal welfare in Nigerian urban environments and support regulatory limits on noise levels near animal housing and livestock markets. Keywords: noise stress, cortisol, antioxidant, oxidative stress, rats.