The phrase 'tons are' is grammatically correct.
You can use this phrase when referring to a large number or quantity of something. For example, "We have tons of apples in the orchard right now."
Millions of tons are produced every year.
Now millions of tons are produced every year as fertiliser.
Furnaces with capacities up to 130 tons are in operation.
A million more tons are on the way.
Three tons are consumed this way at each year's tournament.
AOD converters with capacities up to 160 tons are in operation.
They would take effect once last year's global imports of 27 million metric tons are exceeded.
Of 13 million tons in annual steel imports, about 3.2 million tons are now exempt.
Tons are stolen, countywide — the better to bring gravitas to new construction.
A total of 24 tons are sent to China annually from such mines, according to the secretary general of the Chinese Mining Association in Ghana; 980 tons are not shipped to Shanglin County alone.
Quartz is the only natural silica mineral used in significant quantities; millions of tons are consumed annually by many industries.
