مقاله در مورد رابطه بهداشت حرفه ای و نانو تکنولوژی

nanocommentary: Occupational and environmental

?health and nanotechnology—what's new

In the August 2006 issue of the journal, Seaton explored the occupational health and safety issues in nanotechnology. Analogies were drawn from what was already known about asbestos- and combustion-generated nanoparticles, both of which also fall in the nanosize range. The challenge seen was to get companies to implement reasonable risk control measures to protect their workers even as the industry is still at an early stage of development. It was suggested that while toxicological studies had yet to document definite adverse human health effects, we should proceed with caution and not allow the same tragedy to happen as with asbestos [1]. Two years have since passed. Given the rapid advances in nanotechnology, what new answers do we have to the issues raised by Seaton?

The nanotechnology industry has grown exponentially in the past 2 years. Active research and development in institutions and industries have resulted in new discoveries for nanomaterial applications. A growing number of nanotechnology companies are being set-up around the world, producing >USD$1.1 trillion worth of products in 2007 incorporating nanotechnology [2]. However, research into occupational health and safety in the nanotechnology industry has still to catch up. The most progress appears to have been made in toxicity studies using animal and in vitro models. In a recently published pilot study on mice, granuloma formation was noted within 7 days after intraperitoneal injection of 50 mcg carbon nanotubes, whereas mice injected with control material did not show any granulomatous response [3]. This was similar to what Japanese researchers found that mice given intraperitoneal injections of multi-walled carbon nanotubes (MWCNTs) developed mesothelioma, akin to positive controls which were given intraperitoneal crocidolite [4]. Japanese researchers also recently found that MWCNTs exert greater toxic effect on mouse macrophages than crocidolite. Cytotoxicity was manifested by plasma membrane rupture and the LC₅₀ (lethal concentration for 50% of macrophages) of MWCNTs on the macrophages was 1/25th that of crocidolite [5]. A question that still remains to be answered is whether similar effects will occur in humans and at what exposure levels.

Another area of concern identified by scientists has been the release of nanomaterials in consumer products to the environment. One of the commonest nanomaterials used in consumer products is nanosilver, mostly for its antimicrobial effects. Socks coated with nanosilver are marketed as non-odour forming. However, a study published in June 2008 reported that six types of nanosilver-treated socks leached silver nanoparticles when soaked in distilled water [6]. The rate of silver release varied between the different types of socks, suggesting that the sock manufacturing process may control the release of silver. This study raised concerns that nanosilver released from consumer products may enter wastewater systems and disrupt aquatic ecosystems. While ionic silver is known to be toxic to aquatic life, the effects of nanosilver are still unknown. Action may need to be taken to ensure manufacturers use the right processes to prevent such leaching and to raise consumer awareness on nanomaterial-based products [7].

A Working Party on Manufactured Nanomaterials (WPMN) was formed by the Organization for Economic Cooperation and Development in 2006 and has made substantial progress on coordinating and furthering research into the health and safety issues surrounding the nanotechnology industry. One of their major projects involves the development of platforms through which researchers can exchange ideas and information on human health and environmental safety findings.

To address the problems related to the heterogeneity of nanomaterials, the WPMN is coordinating the testing of a representative set of 16 manufactured nanomaterials for human health and environmental safety effects. Included in the list are silver nanoparticles, single and MWCNTs, titanium dioxide and zinc oxide. The selection was made based on which materials are presently in commerce or close to commercial use, taking into consideration also that other materials may become important in the future [8].

Although there are still no regulations at the federal government level, state and local officials in the USA have begun to take steps to regulate the nanotechnology industry by monitoring the production and storage of nanomaterials [9]. The next US presidential administration is also already expected to give more priority to nanotechnology regulation as well as health and safety research [10]. The National Institute for Occupational Safety and Health has identified critical areas to be addressed in nanosafety research to guide in addressing knowledge gaps, developing strategies and providing recommendations. These include exposure and risk assessment, measurement methods and personal protective measures [11].

In June 2007, the European Commission launched Regulation for Registration, Evaluation, Authorization of Chemicals (REACH). The objectives of REACH include improvement of human health and environment protection from risks that can be posed by chemicals and the promotion of alternative methods for assessment of hazards of substances. Nanomaterials are among the substances covered under REACH [12].

Unfortunately, regulations set by government agencies are still limited by the need for enforcement. Companies themselves need to have a responsible health and safety practice towards new substances that they manufacture or import. A survey in Germany and Switzerland published in January 2008 found that nearly two-thirds of the 40 companies surveyed did not perform any risk assessment on their nanomaterials. Most companies also paid little attention to the issues of end-user and disposal worker exposure [13].

So what can occupational physicians do? In his August 2006 article, Seaton called on occupational physicians to investigate work practices and control measures in research institutions and nanomaterial companies. The same still holds true today. In the face of the continued uncertainty about the human health effects, employees handling nanomaterials in industries as well as in research institutions need to be made aware of the potential risks, without causing them undue alarm.

As mentioned by Seaton, occupational physicians also have a role in advising on the safety of products outside the workplace. Nanomaterial-containing consumer products are becoming increasingly common worldwide. There are now >800 currently on the Project on Emerging Nanotechnologies' inventory [14]. Despite this, public awareness of nanotechnology is still low. A public perception study published by the Yale Law School in March 2007 reported that >80% of subjects did not know anything at all about nanotechnology prior to being surveyed [15].

Occupational physicians would thus be required to keep abreast and update themselves on toxicological and health and safety developments in this growing industry. There is also the need to look beyond the factory fence to consider safety