Four of every 10 San Bernardino County residents speak a language other than English at home.

Spanish is preferred at home by one-third of the county’s 1.8million people ages 5 and older, according to information released this week by the U.S. Census Bureau.

Critics see the increasing use of Spanish as a troubling development.

A spokesman for a group that favors limiting immigration said Americans should be concerned about "the possible Balkanization of the culture.”

"The one thing that’s absolutely essential to congenial human interaction is speaking the same language,” said Rick Oltman, media director for Californians for Population Stabilization. “We need to know what each other is saying so there is understanding.”

Being able to communicate in English is essential to doing well economically, he said.

"If you’re going to be fluent in a language, you’d better be fluent in English if you want a chance at prosperity,” Oltman said.

Education experts don’t see the growth of Spanish as a threat.

"Unfortunately, it has been viewed as a deficit in this country, but bilingualism and multilingualism is a definite asset in business, government and educationally,” said Barbara Flores, a professor of language, literacy and culture at Cal State San Bernardino.

The local trends mirror a language and ethnic shift sweeping through several states.

At least one in five residents of California, Arizona, New Mexico and Texas spoke Spanish at home last year, according to American Community Survey data.

Nationwide, about 35million Americans, or 12.3percent of the population, speak Spanish at home.

The Census Bureau also estimates the foreign-born population last year reached an all-time high of 38 million, representing nearly 13 percent of the population. About 12million were born in Mexico.

California had the most residents born outside the United States at 27 percent. In San Bernardino County, 22 percent of the population, or about 440,000 people, are immigrants. Three-fourths of the county’s foreign-born come from Latin American countries, the vast majority of them from Mexico, the data shows.

The head of a group that supports making English the official U.S. language said government data tends to be used to support more bilingual education, additional bilingual voting materials and increased services to people in Spanish.

"The data is not the issue. It’s the use of this data to impose multilingual mandates on communities,” said Jim Boulet, executive director of Springfield, Va.-based English First. "Once you give special treatment to one language group, speakers of other languages feel discriminated against.”

But Flores pointed to a study by the Pew Hispanic Center last year that showed 88percent of U.S.-born adult children of Latino immigrants speak English very well.

"Their dominant language is definitely going to be English by the third generation,” said Carmen Fought, a professor of linguistics at Pitzer College in Claremont.

Fought said it doesn’t matter how many people speak Spanish.

"English is still the language of power in this country. It’s dominant in every aspect of society,” Fought said.

Lynda Gonzalez, a 46-year-old Bloomington resident, has four bilingual children. Three of them attend college and the fourth is in high school.

"We always speak Spanish to the kids,” Gonzalez said. "It’s important for them not to lose the language and the culture. That’s part of who we are.”