The culprit is a molecule called gliadin, which is found in certain gluten-containing grains and causes symptoms in gluten-sensitive people. The grains that cause the greatest problems are wheat, rye, barley, spelt, and kamut; whereas corn, rice, millet, and buckwheat are generally considered safe.
The Forth Bridge's piers are constructed from 120,000 cubic yards of concrete and masonry, faced with 2 ft thick granite. 200 trains use the bridge every day, carrying 3 million passengers each year. The total painted area of the Forth Bridge is 230,000 sq metres, requiring 240,000 litres of paint.
London's Tower Bridge, which crosses the Thames near the Tower of London is a Bascule bridge whereby two halves of the bridge swing into the air to let tall ships pass underneath. The mechanism is made of steel but encased in stone for the sake of appearance. Naturally the road surfaces are tarmacadam.