Inhalation of iron-abundant gas metal arc welding-mild steel fume promotes lung tumors in mice.

Welding fumes were reclassified as a Group 1 carcinogen by the International Agency for Research on Cancer in 2017. Gas metal arc welding (GMAW) is a process widely used in industry. Fume generated from GMAW-mild steel (MS) is abundant in iron with some manganese, while GMAW-stainless steel (SS) fume also contains significant amounts of chromium and nickel, known carcinogenic metals. It has been shown that exposure to GMAW-SS fume in A/J mice promotes lung tumors. The objective was to determine if GMAW-MS fume, which lacks known carcinogenic metals, also promotes lung tumors in mice. Male A/J mice received a single intraperitoneal injection of corn oil or the initiator 3-methylcholanthrene (MCA; 10 µg/g) and, one week later, were exposed by whole-body inhalation to GMAW-MS aerosols for 4 hours/day x 4 days/week x 8 weeks at a mean concentration of 34.5 mg/m3. Lung nodules were enumerated by gross examination at 30 weeks post-initiation. GMAW-MS fume significantly increased lung tumor multiplicity in mice initiated with MCA (21.86 ± 1.50) compared to MCA/air-exposed mice (8.34 ± 0.59). Histopathological analysis confirmed these findings and also revealed an absence of inflammation. Bronchoalveolar lavage analysis also indicated a lack of lung inflammation and toxicity after short-term inhalation exposure to GMAW-MS fume. In conclusion, this study demonstrates that inhalation of GMAW-MS fume promotes lung tumors in vivo and aligns with epidemiologic evidence that shows MS welders, despite less exposure to carcinogenic metals, are at an increased risk for lung cancer.

Bone turnover associated with antler growth in red deer (Cervus elaphus).

Although it is known that skeletal bone depletion occurs during antler growth in deer, it is not clear whether repletion of the skeleton takes place before or after completion of antler development. This study attempted to correlate repeated scanning electron microscopic measures of ilium and rib bone porosity from six approximately 2-monthly biopsy samples (using back-scattered imaging) and biochemical markers of bone turnover (serum hydroxyproline and osteocalcin concentrations) taken for 11 months with antler growth in six red deer stags. No changes were detected in ilium samples but changes in porosity of rib bones and an elevation of the biochemical markers indicated that skeletal depletion occurred during the antler growth period. However, the decrease in rib bone porosity and decline in markers of bone turnover took place before completion of antler growth, indicating that a considerable amount of skeletal repletion could have occurred whilst antlers were also undergoing bone accretion. This latter finding extends the current view of antler growth being accompanied by a form of reversible osteoporosis in the skeleton by showing that there is a period when the antlers and skeleton are both undergoing net bone formation.