Information, openly available, is a pillar of our democratic society, and never was that clearer than in the moments before the pillars of the World Trade Center came crashing down.

Immediately after witnessing one of the planes crash into the South Tower, my brother logged onto the Internet at his office in lower Manhattan and starting hunting for information. He was looking for an escape route for his wife and 4-year-old daughter, who were in their apartment across the street from the Twin Towers. An architect, he found Web sites that described the towers' structure and dimensions, which helped him think through likely collapse scenarios. He used this information to develop a plan for reuniting with his family and ultimately gaining safe passage by police boat from lower Manhattan.

But who knows if someone else might have sought out this same information for nefarious purposes, such as to plot the attacks themselves?

This is the quandary our nation faces as we struggle to find the right balance between openness and secrecy. It comes at a time in our technological history when extraordinary electronic access to information -- about things such as the performance of drinking water systems and the chemicals used at processing plants -- has become an integral part of the system of public health and environmental protection.

The dangers of disclosure are evident. One anti-nuclear activist found, in a Nuclear Regulatory Commission reading room, a study showing the potential catastrophic consequences if an airplane were to crash into a nuclear power plant and damage the plant's spent fuel storage facility. The government would never want to unwittingly supply the blueprint for such a disaster. But doesn't the public -- especially those people who live near these facilities -- also have a right to understand these risks? Often the public airing of these risks is what ultimately pressures the government or corporations to take action to minimize them.

The debate over the merits of open information versus state secrets came to a head again last week, with congressional authorization of the new Department of Homeland Security. Tucked into this legislation is a controversial section. It exempts from public disclosure any information about infrastructure security vulnerabilities that a private company voluntarily provides to the government. It insulates companies by barring anyone, including the Environmental Protection Agency (EPA), from using these disclosures in civil prosecutions for violations of environmental laws. It also makes it a crime for a federal worker, such as a whistleblower, to disclose any of this information.

A coalition of journalists, environmental groups, scientific researchers, librarians, and civil liberties and consumer watchdog organizations vigorously opposed these efforts as going too far in removing from public scrutiny the potential risks that may exist in communities across the country. The coalition also expressed concern that companies will try to gain unwarranted protection from prosecution for violations of the environmental, health and safety laws by claiming applicability of these provisions.

The battle to ensure safe conditions at the District's Blue Plains sewage treatment plant is one example of the benefits of open information. For years, community activists and neighboring local governments called for the sewage agency to substitute more benign materials for the large quantities of dangerous liquid chlorine kept at the plant for disinfection. If the plant's tanks were breached and chlorine released as gas, it could endanger the lives of thousands in the metropolitan area. Public information about the presence of this chemical was vital to these advocacy efforts, which, finally, after the events of Sept. 11, 2001, succeeded in persuading the District's Water and Sewer Authority to eliminate use of liquid chlorine and use a safer, solid chemical.

In searching for the right balance on these issues, it is essential to remember why the United States has attached importance to public information in protecting our health and environment. In 1984, approximately 2,000 people were killed and more than 100,000 were seriously injured when chemicals leaked from a Union Carbide plant in Bhopal, India. The next year, a leak from a sister facility in Institute, W.Va., sent 135 people to the hospital. These accidents spurred Congress to adopt legislation creating a "right-to-know" program designed to foster public disclosure of chemical safety risks. The law requires companies to disclose their use, processing and storage of toxic chemicals. This information has become increasingly available online, and has become a valuable tool for industry and communities to work together in identifying and reducing risks. In some instances, public scrutiny of toxic emissions has prodded companies into cutting leaks by as much as 50 percent.

The years before 9/11 saw a sharp increase in the amount of public information available, a trend that has now collided with security concerns. Before the attacks, the chemical industry embraced elements of the right-to-know philosophy in its Responsible Care program, an industry code of conduct. During the Clinton administration, the EPA expanded the right-to-know program by doubling the number of chemicals covered, broadening the types of facilities, and lowering the thresholds for reporting on the toxics release inventory. Disclosure requirements now cover areas such as drinking-water violations, so that at-risk populations -- such as the sick or elderly -- would know if they needed to do anything special to be safe. New chemical testing programs provide the public with basic health information about the major chemicals in commerce.

This kind of information has been meeting a growing public thirst for quicker and better environmental information. It also ensures accountability in environmental performance in a way that inspectors in the field -- who, in reality, are few and far between -- cannot. When I first was appointed to work at the EPA in the beginning of 1994, its Web sites received approximately 100,000 hits per year. Last month, EPA sites received 123 million hits. This kind of environmental information also allows environmental management and regulation to be far more results-oriented and performance-based, which is key for dealing with today's complicated environmental problems.

With this vast expansion of environmental information has come new challenges, derived in part from unintended consequences. In 1990, Congress required that corporations draw up "worst-case analyses" of the consequences of chemical accidents and make them public. Later, government and industry realized that these scenarios, including projections about deaths in areas surrounding a facility, would be available to anyone in the world armed with a personal computer and access to the Internet. Once the security implications became manifest, we at EPA worked closely with the FBI's terrorism experts and Congress to amend the law and fashion an approach that would control public access without eliminating it. The EPA created a series of "speed bumps" that restricted the electronic dissemination of this data to the general public. It still allowed local emergency responders to access the information electronically, and provided the public with limited access to hard copies of these analyses at state or government agency public reading rooms around the country.

The events of Sept. 11, 2001, have caused the EPA, other government agencies and the operators of potentially vulnerable sites to reassess the publicly available information on their Web sites. After examining 180 different information resources available online, the EPA removed from its Web site toxic chemical accident and response assessments, known as Risk Management Plans, as well as acute chemical exposure health information, and is currently making this information available only in reading rooms. Other agencies, including the Federal Aviation Administration, the Department of Transportation and its Office of Pipeline Safety, the Department of Energy, the Federal Energy Regulatory Commission, the Nuclear Regulatory Commission, the U.S. Geological Service, the Agency for Toxic Substances and Disease Registry, as well as many states, have likewise removed a significant amount of sensitive information concerning the location and operation of hazardous facilities. Yet these agencies have not articulated -- much less sought input on -- the standards they used in choosing what information to make secret.

Industrial companies need to overcome strong suspicions within the environmental community that they will seek to take advantage of the current situation to fulfill what is perceived to be a long-held desire to gut the right-to-know law and install other loopholes. Environmentalists and community groups cite earlier efforts by many corporate lobbyists to persuade Congress to thwart EPA's expansion of right-to-know reporting through a series of attempted appropriations riders. And they ask -- with some common-sense appeal -- why a business would hide a threat from a facility's neighbors rather than take whatever precautions it can to minimize those threats, such as using less hazardous materials or hardening security.

Community concerns need to be taken seriously because Americans' safety is at stake. More than 32,000 releases of hazardous chemicals have taken place so far this year, according to the National Response Center, the federal government's reporting and response system.

The central trend in environmental protection today is managing information both to expedite regulatory processes and to provide the government and public with new levels of insight and participation. In balancing openness and security, neither advocates for the right to know nor those who stress security have a lock on patriotism. While no one wants to provide a blueprint for terrorists intent on disrupting our nation, the presumption should be one of continued openness, unless a real risk can be demonstrated. The protection of our nation's environment and public health -- through open access to information about toxic risks -- has become an essential American practice. We should all be thankful that activists will monitor carefully whether government and industry abuse the new secrecy provisions of the Homeland Security law. And we should insist on a public accounting of the criteria and processes used by government in making this kind of information secret. Gary Guzy, a lawyer in Washington, served as general counsel of the Environmental Protection Agency during the Clinton administration.