Mechanical, Chemical, Structural, and Radiological Changes in Pigeon Bone, Associated with The Dietary Intake of Nickel Recovery Slag

Abstract

Slag from nickel smelting operations in the Sudbury basin in Ontario, Canada, has become ubiquitous. This material rich in heavy metals such as iron, upon ingestion has the potential to effect physical, radiological, chemical, mechanical, and structural changes in biological systems. In this work, we analyzed the effects of slag ingestion through diet, on several quantitative and qualitative parameters of the tibio-tarsal bones in pigeons (Columbia Livia Domestica). The specimens were maintained on a seed diet and divided into a control group (n = 9) provided (normal) clean limestone grit, and an experimental group (n = 9) provided slag-based grit, both for a period of one year. Their tibio-tarsal bones were harvested for analysis. Quantitative analytical methods included conventional density measurements, caliper-based cortical thickness measurements, bone mineral density measurements using Dual Energy X-ray Absorptiometry (DEXA), calcium and iron concentration measurements using mass spectrometry, and the determination of Young's Moduli and ultimate breaking strength (both in compression) using a universal testing machine (UTM). Qualitative microscopy studies, both optical and electron -including energy dispersive spectroscopy (EDS) -were carried out for both sample groups. A Welch's t-test (single tail) was used to compare means of the seven quantitative parameters between control and experimental samples; in six of these parameters, a statistically significant difference was found (p ≤ 0.05). Microscopy, both optical and electron -coupled with EDS analysis -revealed structural differences in bone between the two groups. Engineering hardness testing of grit types in the dietary components revealed that the slag ingested by the experimental group was approximately twice as hard (Brinell and Rockwell hardness) as the limestone grit in the control group diet. We conclude that slag ingestion through diet in the species examined, is associated with measurable changes in mechanical, chemical, structural, and radiological properties of the tibio-tarsal bones.

The Use of Different Statistical Metrics to Detect Physiological Changes in Metal-Overloaded Avian Bone

“…This anticorrelation is also consistent with our previous work, in which we reported the existence of large cavities visible under electron microscopy (Fig. 3) [4].…”

“…Regarding the very strong anticorrelation between these two parameters in the experimental group (metaloverloaded), this is consistent with our previous work, in which we reported the existence of large cavities visible under electron microscopy (Fig. 3) and Silva's proposition that adding layers of bone thickness in metal-overloaded specimens results in physiological degradation [4,21]. Orban, and Dorrestein et.…”

“…In our previous work, we reported the existence of large cavities visible under electron microscopy examination, as seen in Fig. 3 (JEOL model 6400 Scanning Electron Microscope, JEOL Corp., Tokyo, Japan) [4]. These cavities are consistent with resorptive cavities lined with osteoclasts, and are indicative of cortical discontinuities, foci of woven bone formation, and/or spicules of fibroplasia, all consistent with previously reported histological findings [8].…”

“…The methodology used to obtain the physical measurements used as raw data for this work, as well as the biological aspects of specimen handling and care, have been extensively described and we repeat here only as a brief of summary [4,8]. Previously, we examined changes in pigeon bone associated with the dietary intake of nickel mining slag, which resulted in a condition of metal (mostly iron) overload in the specimens.…”

“…In previous work, we examined mechanical, chemical, structural, and radiological changes in pigeon bone (Columbia Livia Domestica), associated with the dietary intake of nickel recovery slag, which contains approximately 40% iron by weight [4,5]. The specimens were maintained on a seed diet and divided into a control group provided (normal) clean limestone grit, and an experimental group provided slag-based grit -both for a period of one year -after which their tibio-tarsal bones were harvested for analysis.…”