When methyl isocyanate (MIC) is transported in the United States, it is placarded with a red diamond. This identifies it as flammable, not as poisonous, although fumes of this same chemical killed more than 2,000 people in the Dec. 3 leak at the Union Carbide pesticide plant in Bhopal, India.
In the aftermath of the Bhopal leak, this designation for MIC is highlighting some serious questions about the stringency of federal standards for packaging hazardous materials when they are carried by truck, rail, air, and barge.
Because the Department of Transportation (DOT) had determined that flammability, rather than toxicity, was MIC's major hazard, the design standards of the rail tank cars and drums used to ship it are substantially weaker than those required to transport radioactive material or the 26 chemicals, such as hydrogen cyanide, that are on the DOT's most stringent ''poison A'' list.
James Burnett, chairman of the National Transportation Safety Board, criticized this classification in a letter to DOT's Research and Special Programs Administration and expressed concern that pertinent federal regulations may generally be too lax.
''Fire is the major killer in transportation, not poisoning,'' replies Lee Santman, head of DOT's Hazardous Materials Bureau, which sets these standards. The effectiveness of current regulations is reflected by the relatively low frequency of incidents involving hazardous materials, Mr. Santman maintains. The estimated number of shipments of hazardous cargo is from 100,000 to 250,000 daily. In the last three years, an average of 320 people have been injured and 16 people have died in related incidents annually.
Even before the Indian accident, growing public concern about the issue had prompted increased scrutiny of current practices.
''There really isn't any attempt to regulate materials based on their hazard, '' says Julie Jordan, who follows this issue for the National Conference of State Legislatures.
Santman disagrees, but does agree that the problem of assessing a given material's hazard is far from trivial.
''There is a lot of subjective judgment involved,'' he says. How do you determine the risk of a truckload of butane lighters? Or a chemical like MIC, which is relatively nontoxic in certain forms, but can become acutely poisonous in the right conditions? he asks.
''Chemicals can come in so many different formulations. What is difficult to address is material with two or three different hazard classifications,'' adds Steve Brown, a hazardous material specialist with the California Highway Patrol.
From an emergency response perspective, the DOT has tackled this problem by assigning a four-digit code to each hazardous material. Turning to this number in a 500-page guidebook, police and firefighters can respond to an accident with instructions of the proper steps to take. But it is unclear whether DOT has as successfully coped with multiple hazards in formulating specifications for the containers required.
Federal regulatory efforts in this area date back to the first part of the century and have evolved gradually. In two large volumes, the DOT publishes the technical specifications for the containers, tanks, trucks, and rail cars that must be used in carrying bulk quantities of some 3,500 different hazardous materials.
These designs have evolved largely as the result of mishaps. For instance, several severe rail incidents in 1978-79 led to changes in the design of rail tank cars. New types of couplers were specified that are less likely to puncture adjacent tank cars. Protective shields at each end of the car provided another barrier against rupture. To reduce the danger that a tank would explode when exposed to fire, increased insulation was added to slow the temperature buildup of the material within the tank.
These changes have been credited in part with a recent decline in derailments leading to releases of hazardous materials.
As the railcar experience suggests, the adequacy of federal designs is only tested in real situations.
The DOT has not had a program of crash testing the containers it requires, so the precise conditions that they will withstand are not well known. Some experts , including people within the DOT, advocate switching to a ''performance standard'' approach that would specify the conditions containers must withstand rather than merely specify the details of their construction.
Another improvement that has been suggested is a more systematic collection and analysis of data on transportation accidents.
Currently, this information is not reported to a central location. If it were gathered and regularly analyzed, this might provide early warning of defects in certain types of containers or other significant trends, advocates argue.