Action levels
Physiological quantities linked to the exposure limit values in the tissue are not directly measurable, therefore external reference values (action levels) have been introduced as directly measurable physical quantities. These action levels are derived from the ELVs and allow for a direct comparison with measurable quantities - electric field strength and magnetic flux density.
• Compliance with upper action level implies compliance with ELVs. Upper action levels are derived from internal ELVs, assuming worst case exposure conditions.
• Compliance with lower action level implies simple risk assessment - no measures necessary, except for active implantable medical devices (AIMD).
Corresponding author: Dr. Ljiljana Udovicic, Bundesanstalt für Arbeitsschutz und Arbeitsmedizin, PF 170202, D-44061 Dortmund - udovicic.ljiljana@baua.bund.de - www.baua.de
Introduction
After the European Directive 2004/40/EC on occupational exposure to electromagnetic fields has been adopted, stakeholders raised concerns that it might have an
unnecessary negative impact on technological processes, equipment and workplaces which use high currents or strong magnetic fields, or that it might impede the use of magnetic resonance imaging (MRI) in medicine and research. Additionally, the need for complex and expensive numerical calculations in order to prove whether the
exposure situation at a workplace is compliant with the exposure limit values - as soon as the action values are exceeded - could create a huge burden for small and
medium-sized enterprises. Under these circumstances, the deadline for transposition of the Directive into national law of the member states has been postponed in order to allow a new Directive based on the most recent scientific evidence.
The poster presents a new, easily applicable health and safety concept based on the current scientific and physiological knowledge. The concept addresses workers’
exposure assessment to static and time-varying electric and magnetic fields with
frequencies up to 100 kHz. It has been elaborated by a governmental German group of experts (search internet for: BMAS report FB 400).
Conclusions
The proposed concept
• ensures a high level of health and safety protection of workers with respect to occupational exposure to static and low frequency electric and magnetic fields without imposing unnecessary burden;
• introduces ELVs for PNS for controlled working condition with the reduced safety factor of 2, additionally to those for normal working conditions proposed by ICNIRP, still guarantying health and safety of workers;
• does not need any derogations, in particular for MRI;
• contributes to a simplified risk assessment and therefore supports SMEs without the need for unnecessary and costly measures.
Occupational Exposure to Static and Low Frequency Electric and Magnetic Fields – A New Health and Safety Concept
Hannah Heinrich
1, Georg Hilpert
2, Hannelore Neuschulz
3, Fritz Börner
4, Hauke Brüggemeyer
5, Siegfried Eggert
6, Markus Fischer
7, Klaus Hentschel
3, Ljiljana Udovicic
31
2h-engineering, Hausen, Germany,
2Federal Ministry of Labour and Social Affairs (BMAS), Bonn, Germany,
3Federal Institute for Occupational Safety and Health (BAuA), Dortmund, Germany,
4Institute for Occupational Safety and Health of the German Social Accident Insurance, Sankt Augustin, Germany,
5Lower Saxony Water Management, Coastal Defence and Nature
Conservation Agency, Hildesheim, Germany,
6formerly Federal Institute for Occupational Safety and Health, Berlin, Germany,
7
German Social Accident Insurance Institution for the Energy, Textile, Electrical and Media Products Sectors, Cologne, Germany
Exposure Limit Values – Stimulation of sensory organs
ELVs for stimulation of all sensory organs (ICNIRP-modified)
Nausea and vertigo: not covered by ICNIRP ELVs, safety factor 1
ELVs for magneto- phosphenes, safety factor 1 (ICNIRP)
Lower action levels protect against:
• projectile risk (0 - 1 Hz in a magnetic field),
• micro shocks caused by contact currents (time varying electric fields),
• indirect effects (time varying magnetic fields), exception AIMD.
Risks arising from static and low frequency electric and magnetic fields (up to 100 kHz):
• Stimulation of peripheral nervous tissue (PNS)
• Stimulation of sensory organs (retina, inner ear): magnetophosphenes, nausea, vertigo (transient effects)
• Indirect effects (projectile risk, implants)
Example: lower action levels for magnetic fields
Safety factor 5
Threshold for
projectile risk at 30 mT
ELVs for PNS
Threshold for PNS
Jokela and Saunders, Health Phys. 2011
ELVs for PNS - normal working conditions,
safety factor 5 (ICNIRP)
ELVs for PNS -
controlled working conditions,
proposal - safety factor 2
Threshold for PNS, Lapique’s law
1.2 V/m
3 kHz
Jokela and Saunders, Health Phys. 2011
safety factor 5
safety factor 2
6 V/m
Exposure Limit Values
The relevant parameter in the stimulation of nervous tissue is the membrane potential.
Since only an exposure above the threshold can cause a stimulation, the exposure limit values (ELVs) should be given as peak values of the electric field strength in the tissue and not as rms-values. Otherwise the exposure could be underestimated.
Exposure Limit Values – PNS
Two sets of ELVs for the peripheral nervous stimulation (PNS) have been laid down for
• normal working conditions where the corresponding ELVs must not be exceeded,
• controlled working conditions where ELVs of normal working conditions could be exceeded and specified written working procedures, trained and advised personal, presence of a second authorized person become necessary.
Health &
Safety Concept
EMF exposure
Risk 5 % applications
95 % applications (low EMF
exposure)
Exposure limit value Upper action level
Lower action level
EMF exposure
Risk
Exposure limit value Upper action level
Lower action level Safety related risks
Organisational measures, information required
No risks
No further action or measures required
Unacceptable risks
Compliance check
Example: upper action levels for magnetic fields
EMF exposure
