Histological Changes in the Lungs and some Haematological and Biochemical Changes in Wistar Rats Following Exposure to Fly Ash Dust

Abstract

Background: Fly ash dust is a harmful air pollutant that poses a major environmental and health risk. Previous research has linked fly ash dust to respiratory tract disease but its effects on the lung are not well understood. We aimed at investigating body weight, lung histoarchitecture, and haematological and biochemical changes in Wistar rats exposed to fly ash dust.

Methods:Twenty-four Wistar rats (12 males, 12 females), weighing 250g-280g, were randomly assigned into 4 groups of 6 animals each. Group A rats were placed in a fly ash dust-free chamber while Group B - D rats were exposed to various concentrations of fly ash dust dispersed from 5g, 10g and 20g of fly ash, respectively. The weights of the animals were recorded weekly and body weight gain computed. At the end of 28^th day of exposure, the rats were weighed and euthanized under chloroform anaesthesia. Blood samples were collected through cardiac puncture into plain specimen bottles for biochemical analysis and into EDTA anticoagulant bottles for haematological analysis. The lungs were harvested and processed for histological examination. The obtained data were analyzed using the one-way Analysis of Variance, with level of significance set at P<0.05.

Results: Exposure to fly ash dust caused significantly reduced weight gain and haematological alterations in rats including decreased lymphocytes, haemoglobin, and red blood cells. Biochemical analysis revealed increased manganese, urea, and creatinine levels, indicative of manganese poisoning and renal impairment. Additionally, low serum bicarbonate (HCO₃^-) levels suggested acidosis. Histopathological examination confirmed normal lung architecture in the control group. There were observable histological variations in the lung architecture of the exposed rats (Groups B-D) which include bronchiolar ulceration, activated lymphoid follicles, and patchy alveolar collapse (evidence of pneumonitis). Given the similar biological responses, these effects of fly ash dust on rats can be reasonably extrapolated to humans, highlighting the importance of protective measures for individual occupationally exposed to fly ash dust.

Conclusion: Fly ash dust caused body weight loss, histopathological changes in lung tissue, haematological and biochemical derangements which are capable of compromising lung, haematological, biochemical and renal functions, potentially resulting in fatal outcomes.