The phrase "are large concentrations of" is correct and usable in written English.
It can be used when discussing the presence or abundance of something in a particular area or context.
Example: "In the ocean, there are large concentrations of plastic waste that pose a threat to marine life."
Alternatives: "are significant amounts of" or "are high levels of".
Famine conditions exist in two large regions of Somalia, as well as three smaller areas, including parts of Mogadishu where there are large concentrations of displaced people.
Like their Indian and Chinese counterparts on Long Island, many Korean transplants have come from Queens, where there are large concentrations of Korean immigrants in Flushing and Bayside.
There are large concentrations of fishponds in the northern and eastern parts of the island, and mineral deposits include coal and copper.
Investigators have discovered a major potential metallic source on the deep ocean floor, where there are large concentrations of manganese-rich nodules along with minor amounts of copper, nickel, and cobalt.
In cities where there are large concentrations of such immigrants in science and engineering, overall wages tend to go up, especially among college-educated American residents, and eventually, so do housing prices, according to a study by Giovanni Peri, an economist at the University of California, Davis.
There are large concentrations of business premises in the south of the town and around the town centre.
In the fertile delta regions of southeast Viti Levu, however, there were large concentrations of population.
In all the towns and cities, there were large concentrations of Yiddish-speaking Jews.
The Czech events weakened the position of the Habsburgs in Silesia, where there were large concentrations of ethnically Polish inhabitants, whose ties and interests at that time placed them within the Protestant camp.
The clinical limitations with many in-vitro studies are that large concentrations of aspirin are required to create a local effect.
General Franks said that the Iraqi Army had placed major weaponry in civilian neighborhoods of Basra, but there were no large concentrations of Iraqi forces there.
