OSHA Hazard Information Bulletins
September 5, 1990
| MEMORANDUM FOR: |
REGIONAL ADMINISTRATORS |
| THROUGH: |
LEO CAREY
Director
Office of Field Programs |
| FROM: |
THOMAS J. SHEPICH
Director
Directorate of Technical Support |
| SUBJECT: |
Safety Hazard Information Bulletin on Radiofrequency
Radiation-caused Burns |
The Directorate of Technical Support issues Hazard Information Bulletins
(HIBs) in accordance with OSHA Instruction CPL 2.65 to provide relevant
information regarding unrecognized or misunderstood safety and health
hazards, and/or inadequacies of materials, devices, techniques and
engineering controls. HIBs are initiated based on information provided by
the field staff, studies, reports and concerns expressed by safety and health
professionals, employers and the public. Information is compiled based on a
comprehensive evaluation of available facts, literature and in coordination
with appropriate parties. HIBs do not necessarily reflect OSHA policy.
The San Francisco Regional Office has brought to our attention a potentially
serious hazard involving burns on longshoremen caused by radiofrequency
radiation. Two hazards were noted at this location. The burns were
apparently caused by spark discharges from crane cables. Also present was an
induced-current grasping hazard.
The longshoremen were working on a pier that is located in close proximity
to several AM radio station transmitting towers. The radiofrequency
radiation emanating from the transmitters induces electric currents in the
longshoring operation cranes' cables due to the cables acting as antenna
receptors to the radiation. The OSHA Health Response Team measured currents
as high as 200 milliamps (mA). The American National Standards Institute C95
committee is considering a limit for this type of grasping current hazard of
100 mA. Measurements also indicated that electric field strengths in the
general vicinity of the ship were on the order of 10 volts per meter.
However, this is well within the ANSI C95.1 - 1982, Safety Levels with
Respect to Human Exposure to Radio Frequency Electromagnetic Fields, 300 kHz
to 100 GHz, limit of 632 volts per meter for AM radiofrequencies. Because of
this induced current and an open circuit voltage from cable end to ground
measured at approximately 300 volts by the Health Response Team, spark
discharges occur just before and after grasping the cable. These discharges
have resulted in burns.
Controls involve either isolating the crane hook from the crane cable and
block assembly by an insulator or grounding the crane cable with a ground
chain or wire. Either control has drawbacks. Insulators or insulated blocks
are expensive and can affect the lift capability of a crane. Moreover, an
isolated hook cannot prevent inadvertent employee contact with the crane
cable itself. A grounding chain would have to be located manually with each
individual lift thereby inviting inadvertent contact. Failing these
controls, personal protective equipment in the manner of rubber-insert
leather gloves, long sleeve shirts, safety helmets and safety glasses should
be employed.
Please distribute this bulletin to all Area Offices, State Plan States and
Consultation Projects.
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