DETROIT — The salacious instant messages to congressional pages that led to Rep. Mark Foley's downfall in September should have caught the attention of millions of workers and employers.

It was a high-profile example of a growing problem at work: Employees have become so comfortable using e-mail, the Internet and instant messaging that the negative consequences of mixing work, play and technology are catching up.

Numerous surveys show that firings as a result of improper e-mail use have become more common in the last five years.

A 2006 survey by the ePolicy Institute in Columbus, Ohio, showed that 26 percent of 416 companies participating in the survey have fired someone for inappropriate use of e-mail, up from 25 percent in 2004 and 21 percent in 2001.

The trend has coincided with the increased use of company e-mail monitoring, firms routinely blocking questionable Web sites and the widespread introduction of e-mail use policies.

"People have this incredible belief that their e-mail is private and that employers are not allowed to monitor it," said Kristin Byron, assistant professor of management at the Whitman School at Syracuse University. "The reality is that employers can monitor e-mail.

"It makes sense to me," she added. "People do things that are pretty dangerous. They have to protect their business."

Mia Hawkins, a case manager at the Michigan Department of Human Services in Warren, said she uses her work e-mail strictly for business, in part because of her employer's constant reminders.

"They make sure they reiterate company policy constantly, and every year, they make us sign a contract about appropriate e-mail use," said Hawkins, 37, of Eastpointe, Mich. "Whether it's verbal or written, we are constantly getting reminders from directors and department heads."

And because e-mail has made higher-ups more accessible than ever to rank-and-file employees, Byron advises workers to think hard before striking the send key.

"People forget that you have to be courteous, polite, include a greeting, a closing, and make it clear what you're referring to," Byron said.

Workers also often forget that e-mail doesn't just disappear after they delete it from their inboxes. The evidence sticks around on computers. E-mail remains company property long after workers kill the messages. Most companies routinely archive e-mails for a specific amount of time.

A recent survey conducted by the Society for Human Resource Management showed that 58 percent of human resource professionals said their organizations have increased monitoring of employee Internet use. Duane Marshall, CEO and president of Innovative Technology Group Services in Shelby Township, Mich., said the trend to increasingly monitor e-mail and Internet use has played out in his business.

"When we first started, very few people asked us to monitor e-mail or instant messaging, but employers are now realizing that this is a problem," Marshall said, adding that such services now represent 70 percent of the company's business.

"Employers are paying them to perform a function, and they're at work doing online shopping, gaming, trading stocks and checking out pornography when, in fact, they should be working. Not only are they not performing, but they're using company resources to not do work," he said.

This is an increasing concern for employers, said Nancy Flynn, executive director of the ePolicy Institute.

The institute's 2004 employee e-mail and Internet survey found that 86 percent of employees engage in personal e-mail and 10 percent of those who do so spend four or more hours a day e-mailing.

"That's half the work day," Flynn said.

Flynn said that fear of lawsuits against the company — for reasons of discrimination or sexual harassment — is a growing reason employers are becoming more vigilant about nonessential e-mail use. "E-mail is the electronic equivalent of DNA evidence," Flynn said.

Melanie LaFave, a partner at the Southfield, Mich., law firm Jaffe Raitt Heuer & Weiss PC, said that more firms are seeking guidance in writing employee e-mail policies. She said it's essential to have a firm policy on e-mail and Internet use.

"As long as they have a policy in place that says that everything in the system is company property, it should be difficult for an employee to make a claim," LaFave said.