MERCURY:
Potentially Grave "Potentially grave" is how a 10-member scientific team describes the problem of mercury contamination in the U.S. The team's 97-page report, "Hazards of Mercury," was released last week by the Department of Health, Education, and Welfare and the Environmental Protection Agency. Among its recommendations: curbs on commercial mercury uses and an immediate, intensive program by the U.S. to decontaminate waterways that contain mercury deposits. There's little likelihood that cases of overt mercury poisoning from consumption of fish or other food products in the U.S. will be found, according to the group headed by Dr. Norton Nelson, director of the institute of environmental medicine of New York University. The group concludes that the interim federal guideline for mercury in fish of 0.5 p.p.m. is a "sound basis for the protection of
Use of mercury will expand moderately in near term Outlet
Consumption
(tons)
1969a
1974-75^
Agriculture Amalgamation Catalysts Dentistry 0 Electrical equipment Chlor-alkali plants Laboratory usesb
102 7 112 116
Industrial controls b Paints Paper and pulp Pharmaceuticals Other usesd
265 370 21 27 368
Not accounted for e TOTAL
42 3006
101 9 89 144 863 869 79 351 407 9 25 226 na 3172
710 788 78
a Bureau of Mines, b National Materials Advisory Board. c Includes redistilled mercury, d Includes purchases for expansion and new chlor-alkali plants. e Mercury, chiefly from secondary recovery—uses not specified, na = not available. Source: HEW Study Group on Mercury Hazards
health." But the group cautions that the margin of safety may not be large and that there are uncertainties over the hazard when large amounts of contaminated fish are eaten. The report attaches urgency to finding out whether subtle health effects are present from mercury pollution and to using all possible means to reduce exposure to mercury immediately. A principal recommendation calls for terminating use of all alkylmercury pesticides and severely restricting use of all other mercurial pesticides to demonstrated need. 10 C&EN JAN. 25, 1971
Chemical industry uses of mercury are also singled out for controls in the report. All industrial users of mercury, the report states, and particularly those operating chlor-alkali plants and those using mercury catalysts, should be required to reduce their discharges of mercury into the environment to levels approximating background levels of the metal. Other sources of mercury contamination or exposuresuch as discarded electrical equipment, chemicals, paints, cosmetics, pharmaceuticals, sewage, and fossil fuels—need to be identified and brought under control. Even if these discharges of mercury are completely eliminated, existing deposits in sediments will continue to yield the highly toxic methylmercury to waters for decades to come, the report estimates. Decontamination, therefore, is urgently needed and the scientific team calls for extensive studies involving laboratory to large-scale pilot experiments, pointing out that Sweden has already launched an extensive program. The Swedish program involves studying three methods of decontamination: covering the sediments with fresh finely divided materials with high adsorptive affinity; burying the sediments with inorganic inert materials; and removing the mercury-bearing sediments by dredging or pumping.
PROCESS CONTROL:
Low-Cost Computer A reduction to one tenth the cost of software for digital process control marks Fisher Controls Co.'s entry into the digital control field. Almost a year ago, Fisher entered the computer process control field with ac2—analog control center. And last week, the Monsanto subsidiary introduced dc2— digital control center. Fisher will produce, market, and service both systems, which were developed by Monsanto. (Monsanto bought the process control firm—then named Fisher Governor Co.—in August 1969.) dc 2 was designed specifically for process control applications, Fisher product manager J. Bruce Duncan explains. "This unique marriage of hardware and our new control language pc 2 provides the lowest total user cost for digital control." Typical hardware cost for dc 2 will range from $40,000 to $80,000 with 25 to 75 control loops. Software costs about an additional $5000, which is about one tenth the cost of software for other systems, Dr. Duncan points out. The new pc 2 language was also developed just for process control applications. According to Fisher, pc 2 is a simplified language that a process con-
Fisher Control's Duncan Marriage of hardware and language
trol engineer can learn and use in about 20 hours. Software has been the bane of digital process control, Dr. Duncan notes. "Not only has it often exceeded the cost of hardware, but also program languages required specialists, people not involved in understanding of process control problems. With just 230 statements, pc 2 can equal the capability of 1000 statements in other languages." Fisher claims the dc 2 hardware takes over as much as possible of the routine programing function. No costly programing is required to get input data into memory, which Fisher has dubbed a "free-running front end." No programing is required to get outputs to the process, either. All execute and support instructions for pc 2 are packaged and wired into the hardware so there is no way a user or his program can alter it. The package eliminates need for disks and d r u m s keeping dc 2 as simple as possible, Dr. Duncan explains. "Simplicity is the key to dc 2 ," he adds. "The hardware is in modular units so the system is easy to install, expand, and maintain." Fisher's entry into computer process control pits it against some of industry's giants—IBM, Honeywell, General Electric, and Foxboro. Although minicomputers are being sold by most of Fisher's competitors, price and simplicity will be Fisher's battle cry as it takes on the more entrenched firms in earnest since it now has both analog and digital units. "Can an old-line process control firm successfully step into the electronics age?" might be the pertinent question. Fisher's motivation is simple: The market for valves and similar type control equipment is growing at a 7% per year rate while the computer process control market moves ahead at 15% per year.
