Read the passage excerpt from 'The Iron Docks of Duluth': "Fourteen-year-old Thomas leaned against the damp wooden railing of the ore dock, watching the massive steamship *Superior Star* glide into Lake Superior's harbor. Iron ore, mined from the Iron Range miles to the north, poured down the steep steel chutes into the vessel's hold with a sound like continuous thunder. Red dust floated through the chilly morning mist, coating Thomas's heavy wool cap and worn leather gloves. His father had worked on these docks for twenty years, and today was Thomas's first official shift as an apprentice tally clerk. He clutched his notebook tightly, determined to prove that his eye for numbers was as sharp as any veteran dockworker's." Based on the excerpt, which detail best supports the inference that dock work in 1910 Duluth was physically intense and dusty?