What remains if you take the glass lenses and filters out of a microscope or a theodolite? Or the glass-ceramic scales from a 3D computer numerical control (CNC) measuring machine?
Why should the availability of optical materials be a problem, considering the growing enthusiasm experts and politicians have developed for photonics, especially in the European Union?
The EU has recognized photonics as a key enabling technology (KET) that supports the general targets set out in the Horizon 2020 research and innovation program for Europe: Competitiveness in excellent science, industrial leadership, and solutions to societal challenges.
Other EU policies are making the world safe against hazardous substances that may be toxic, carcinogenic, or mutagenic and enabling better recycling of electronic waste by removing hazardous substances from the electronic devices from the very beginning.
Who could disagree with these goals? Yet, two European Union regulations, REACH and RoHS, endanger the short- and long-term availability of optical materials, which are vital for general technology, research, and development, particularly in medicine, life sciences, computer technology, safety, and security.
REACH is the regulation on registration, evaluation, authorization, and restriction of chemicals. It controls the production and use of chemical substances such as arsenic oxide and boron oxide because of their potential impacts on human health and the environment.
Arsenic oxide is commonly used as a marginal but important constituent in UV detectors, microscopes, telescopes, metrology optics, and low-expansion glass ceramics. However, arsenic oxide will be prohibited for use as a raw material in optical systems after May 2015. Its use will remain allowed as a so-called intermediate substance if the material properties of the substance are substantially changed and made non-hazardous, as does occur during the glass-production process.
RoHS, the regulation of certain hazardous substances used in electrical and electronic equipment, restricts or prohibits the use of mercury, lead, cadmium, chromium VI, and the flame retardants polybrominated biphenyls (PBB) and polybrominated diphenyl ether (PBDE) in the production of electronic and electrical equipment. Although PBB and PBDE play no role as optical materials, prohibition of lead and cadmium will lead to the loss of many essential properties of specialty glass such as refraction and filtering.
These regulations would impair the performance of optical systems strongly if not preventing it totally.
Lead arsenic oxide, for example, is crucial in the making of fluorescence microscopes, and cadmium is needed in laser safety goggles, infrared cameras, bar-code readers, semiconductor crystals, and other devices.
Because of the extreme leverage effect of optical systems, these regulations would be very harmful for the Horizon 2020 program.
Optical materials vital to industry
Around the year 1600, optics gave a boost to science with the inventions of the telescope and the microscope. However, for about 150 years, the achievable image magnification with these instruments could not surpass a factor of 10.
With only one type of glass, it was not possible to eliminate the limiting color blur.
In the 1750s, a new glass type, the lead-containing flint glass, made optical systems possible with better color imaging, thus gaining another factor of 10 in magnification.
Another 130 years would pass until the next and final factor of 10 opened the micro world for biology, medicine, and general technology, with Otto Schott introducing boron oxide, barium oxide, and phosphorus oxide into glassmaking in the 1880s.
The large variety of optical materials now becoming available with high reproducible quality was one of the key enabling factors for the incredible progress humankind has made since then.
Today, virtually all industry relies on high-end optical systems. These systems provide key functions for research, diagnosis, surveillance, and quality assurance in medicine, scientific research, general industry, safety installations, and environmental monitoring.
They are crucial for the automotive, aviation, shipbuilding, and road- and building-construction industries. Even the food industry needs optical-measurement equipment for quality inspection and machine alignment.
Optical systems are ubiquitous in metrology and not replaceable. What cannot be measured cannot be manufactured. So, remove optics and we are back in Galileo’s time.
Regulations have conflicting objectives
These regulations have led to an unnecessary conflict of objectives: Safety of health and the environment against technological progress.
Optical materials need a considerable variety of substances to provide all required properties for high-end systems. Among them are lead oxide, arsenic oxide, cadmium oxide, boron oxide, and other substances that might be hazardous under certain circumstances.
Admittedly, careless use of these substances cannot be allowed. On the other hand, for many years, they have been used responsibly under strict safety regulations for glass production.
Moreover, once molten into glass, these substances become part of the glass matrix on the atomic level and thus are removed from bioavailability in general.
The removal of lead from gasoline many years ago was an important step for human health and the environment. However, the removal of lead from optical glass would have hardly any effect at all in this respect. Instead, the lack of lead causes big problems, for example in microscopy.
Demise of high-end optical systems?
The EU’s REACH lists “substances of very high concern” (SVHC) that may be hazardous for living beings. Each substance on this list is assigned a date after which its use in production is prohibited.
The “sunset date” for arsenic oxide is 21 May 2015.
Lead oxide, boron oxide, and cadmium oxide are on a second list, the so-called SVHC-candidate list. A decision on when or if they will be prohibited is expected soon.
All these substances are needed as raw materials for optical materials. With arsenic oxide, lead oxide, and boron oxide forbidden, optical glasses will be almost eliminated. Of 120 glass types in the SCHOTT catalog, only five would be permitted under REACH in the near future.
Everybody in the optics world knows that this will mean the end of high-end optical systems.
The Abbe diagram shows the optical glasses in the current SCHOTT catalog (120) and the remaining glass types (five) if arsenic oxide, lead oxide, and boron oxide are prohibited.
Replacement materials for consumer optics are inferior
Many companies replaced lead and other hazardous substances in consumer optics in the 1990s. Arsenic oxide was replaced by antimony oxide, and lead oxide by titanium oxide, niobium oxide, and barium oxide. These were successful replacements from a technical point of view.
To determine if an N-BK7-type glass, where 0.2% of arsenic oxide has been replaced by 0.3 % of antimony oxide, is really an environmental benefit, however, may be left to the reader.
The classical flint glass type SF57 containing lead arsenic is far superior to lead-arsenic-free variants. SF57 and its lead-arsenic-free variant N-SF57 have the same refractive index 1.84666 and dispersion (Abbe number 23.8) but very different transmission in the blue-violet wavelength range. The dashed line at 400nm divides visible light from UV-light.
Lead oxide is present in up to 75% of classical flint glasses. It can be removed completely. However, even with long and intensive research, no compositions have been found that have the same high transmission in blue-violet light as the lead glasses.
Using only lead-free glass in microscopes thus cuts away an important part of the spectrum. Rigid endoscopes have a glass light path of 400 mm, sometimes even 600 mm. Images from the abdominal cavity from these lead-free instruments will be dark, with hardly any color contrast.
If you are to be exposed to minimally invasive surgery, ask the doctor if s/he uses lead-free glass in his/her endoscope. And if s/he does, stand up and run!
There are many other special optical materials where unique functions require the use of hazardous substances. Finding replacements requires significant research and development effort, which in many cases will not be economically feasible.
Plus, there is no future scenario upon which glass manufacturers can rely. The REACH SVHC-candidate list is continuously growing.
If an optical systems manufacturer replaces one hazardous raw material with a substance that is presently not on the list, there is no guarantee that the replacement will not appear later on the list.
The F2 glass type widely used for endoscopes contains 45% PbO. It shows high transmittance over total wavelength range even at the 400mm glass path typical for surgical endoscopes The N-F2 (lead-free variant of F2) has a low transmittance, which leads to dark image and does not allow clear distinction of different tissue colors. This could result in a higher risk of cutting into the wrong tissue.
Bulk glass pieces are nonhazardous
Optical glasses, filter glasses, glass ceramics, and infrared materials are molten from well-defined mixtures of raw materials. During the melting process, the raw materials react and create a new chemical substance totally different from the starting materials. The physicochemical, toxicological, and ecotoxicological properties of the substance glass are totally different from those of the raw materials or oxides.
In the state of bulk pieces, glass is of no hazard at all.
The raw-material supply, melting process, and subsequent transforming of the glass substances to optical elements like lenses and prisms are done under strictly controlled environmental, health, and safety procedures and are enforced by permanent surveillance and regular auditing.
Moreover, the total production volume of inorganic optical materials is very small. The total world production is 10,000 – 20,000 tons. Compare this with polycarbonate at 2 million tons, lead at 10 million tons and steel at 1.5 billion tons.
Optical designers need steady supply of raw materials
Optical systems for professional use — and nowadays even for consumer applications — are designed for utmost imaging performance for a wide wavelength range. Such applications require a variety of high-quality glass types.
Industrial optical systems typically need two years from initial design to first glass purchase and are used for 10 years (even longer in defense applications). Designers must be able to rely on the long-term availability of the materials they use.
Since 2005, the German industrial photonics federation SPECTARIS, supported by its more than 100 German member companies, especially SCHOTT and Carl Zeiss as contributing partners, succeeded two times in obtaining exemptions from the EU RoHS regulation for lead-containing flint glasses and cadmium-containing filter glasses. The current exemption expires in July 2016.
SPECTARIS and its partners, including the consulting company ERA Technology (UK), have already started the next application for prolongation.
EU REACH and RoHS only seem benign
EU REACH accepts glass in general (for windows, bottles, etc.) as a substance of variable composition, without the need for registration. Raw materials are classified as “intermediate substances” because their properties completely change during melting. So at present there doesn’t seem to be an acute reason for concern. However, this interpretation is not safe.
The hazardous substances are not explicitly or officially recognized by authorities as intermediate substances for optical materials production. So the declaration by industry that these are intermediate substances may be subject to lawsuits, creating uncertainty among optical companies.
Moreover, more and more additional substances must be used under the declaration of intermediate substances, even further increasing the possibility of lawsuits.
It is astonishing how the EU releases regulations that strongly endanger the only remaining supplier of optical glasses in Europe. On one hand, European regulators strongly support photonics, while on the other hand eliminating its fundamental materials and undermining the strategic importance of optical glass companies.
Inventing fancy new materials won’t secure the future of optical glass in Europe. Existing materials must also be preserved. European regulators simply did not know the ramifications of these rules. And the photonics community, up to now, has been unable to explain such a complicated subject, especially with very unpopular words like arsenic, lead, and cadmium. However, ignoring the problem or kicking the can down the road will cause an even more serious predicament.
And – non-Europeans: Don’t feel safe. Other countries tend to utilize EU regulations for their own legislation.
Photonics industry recommendations
The optical materials optical glass, filter glass, and optical glass ceramics must be taken completely out of the scope of RoHS.
All chemical raw materials needed for the manufacturing of optical materials must be classified “intermediate substances” with legal certainty to guarantee their future availability.
The problems with RoHS and REACH were presented to the Science and Technology Options Assessment (STOA) committee at the European Parliament in February.
To the author’s impression, it was the first time that the message was received by EU officials, with feedback that they have understood and are also concerned about the situation. But the situation is not yet resolved. The future development must be closely monitored and followed up by the optics community.
Details on REACH and RoHS
The EU regulation No. 1907/2006 concerning the registration, evaluation, authorization, and restriction of chemicals (REACH) addresses the production and use of chemical substances and their potential impacts on both human health and the environment.
In its annex XIV, REACH lists substances of very high concern (SVHC) and their “sunset dates” from which market placement and use of the substance will be prohibited unless an authorization is granted.
The latest update of this annex is given in regulation No. 125/2012 of 14 February 2012.
Glass is accepted as a UVCB substance (substance of unknown or variable composition).
Intermediate means a substance manufactured for and consumed in or used for chemical processing in order to be transformed into another substance.
The EU directive 2011/65/EU on the Restriction of the use of certain Hazardous Substances in electrical and electronic equipment (RoHS II or RoHS-recast) restricts (with exceptions) the use of the four elements mercury, lead, cadmium, and chromium VI in the production of electronic and electrical equipment.
It is a sub-regulation to the Waste Electrical and Electronic Equipment Directive (WEEE) 2012/19/EC for collection, recycling, and recovery of electrical goods and for reducing toxic electronics waste.
–SPIE Fellow Peter Hartmann is director of market and customer relations for SCHOTT. He has served on the SPIE Board of Directors and presented a paper on the RoHS regulations at SPIE Eco-Photonics in 2011. Hartmann is a cochair of SPIE Photonics Europe, to be held in Brussels 14-17 April, where he and Wenko Süptitz of SPECTARIS will discuss the REACH and RoHS regulations. (View photonics industry program at SPIE Photonics Europe 2014.) Hartmann has a PhD in physics from Max-Planck-Institut Mainz centered on the development of scintillation glasses. He wishes to thank Thea Marcoux, head of SCHOTT’s marketing department; Uwe Hamm of Carl Zeiss; and Süptitz for assistance in preparing this manuscript.