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Occupational exposure to Cr(VI) compounds in a number of industries has been associated with increased risk of respiratory system cancers [ATSDR ].
Baetjer was one of the first to review the literature presented prior to on the occurrence of cancer in chromate-exposed workers [Baetjer ].
The first epidemiological study of chromate production workers in the United States that demonstrated an association with lung cancer was conducted with 1,445 workers in seven plants engaged in the extraction of chromates from ore from to . The percentage death due to cancer of the respiratory system was 21.8%; the percentage expected was 1.4% [Machle and Gregorius ].
In another key epidemiological study involving workers at a chromate production plant who had worked at the plant for more than 1 year from to , the percentage of deaths due to lung cancer was 18.2%; the percentage expected was 1.2%. For the 332 workers first employed from to , the percentage of deaths due to lung cancer was close to 60% of all cancer deaths, with a latency period of approximately 30 years [Mancuso ; Mancuso ].
Studies of workers in the chromium pigment, chrome-plating, and ferrochromium industries showed a statistically significant association between worker exposure to Cr(VI) and lung cancer [Langard and Norseth ; Sheffet, Thind et al. ; Frentzel-Beyme ; Langard and Vigander ; Davies ; ATSDR ].
In addition to lung cancer, a number of epidemiological studies of workers in chromate industries also showed significantly increased risk for nasal and sinus cancers [ATSDR ].
On the basis of these and other studies, the U.S. Environmental Protection Agency (EPA) and the International Agency for Research on Cancer (IARC) have classified inhaled Cr(VI) as a known human carcinogen [IARC ; EPA ]. The World Health Organization (WHO) has determined that Cr(VI) is a human carcinogen. The Department of Health and Human Services (DHHS) has determined that Cr(VI) compounds are known to cause cancer in humans [ATSDR ].
Lung cancer risk in relation to airborne levels of Cr(VI) was analyzed for chromium chemical production workers and a dose-response relationship was observed in that long-term workers had a higher lung cancer risk than short-term workers [Hayes, Lilienfeld et al. ]. An analysis of lung cancer risk suggests a potential excess risk of death from lung cancer among U.S. workers exposed to the previous permissible exposure limit (PEL) for Cr(VI) of 52 µg/m³ [Braver, Infante et al. ]. More recent studies also disclosed excess risk of lung cancer death resulting from occupational exposure to Cr(VI) compounds [Gibb, Lees et al. ; Park, Bena et al. ].
Stratified analysis of lung cancer mortality showed a trend of increasing mortality with higher cumulative exposure levels. The analyses stratified by duration of employment and time since first exposure indicate a consistency of results among those employed the longest and with the longest elapsed time since first exposure. The latter suggests a latency period of approximately 20-35 years, which is compatible with other research [Luippold, Mundt et al. ].
Carcinogenicity appears to be associated with the inhalation of the less soluble/insoluble Cr(VI) compounds. The toxicology of Cr(VI) does not reside with the elemental form. It varies greatly among a wide variety of very different Cr(VI) compounds [Katz and Salem ].
Epidemiological evidence strongly points to Cr(VI) as the agent in carcinogenesis. Solubility and other characteristics of chromium, such as size, crystal modification, surface charge, and the ability to be phagocytized, compounds might be important in determining cancer risk [Norseth ; Langard ; Gad ].
In addition to the occupational studies, a retrospective environmental epidemiological study was conducted in residents of a county in Sweden where two ferrochromium alloy industries are located. No indication was found that residence near these industries is associated with an increased risk of lung cancer [Axelsson, Rylander et al. ].
A number of chronic inhalation studies provide evidence that Cr(VI) is carcinogenic in animals [ATSDR ].
No evidence exists to indicate that Cr(III) can cause cancer in animals or humans [IARC ; EPA ].
Mechanism of Cr(VI)-Induced Carcinogenicity
The mechanism(s) of Cr(VI)-induced carcinogenicity is not completely understood. The toxicity of chromium within the cell may result from damage to cellular components during the hexavalent to trivalent chromium reduction process, by generation of free radicals, including DNA damage [ATSDR ]. Recent studies indicate a biological relevance of non-oxidative mechanisms in Cr(VI) carcinogenesis [Zhitkovich, Song et al. ].
05 August
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The world of industrial materials is vast and fascinating, but few are as interesting and versatile as chromium carbides. These compounds, formed from chromium and carbon atoms, stand out for their extraordinary mechanical properties and are essential in various sectors, from industrial chrome plating to the aerospace industry. Their synthesis and deposition techniques are key to their success in a wide range of applications.
Chromium carbides and their main properties
In the landscape of metal carbides, chromium carbides are particularly appreciated for their exceptional properties. Not only do they have superior wear resistance compared to other materials, but they also have excellent mechanical properties that make them ideal for high-stress applications.
READ ALSO: Corrosion protection in the aerospace sector
Synthesis of chromium carbides
The synthesis process of chromium carbides involves complex heat treatments and sintering processes. These stages ensure the formation of a high-quality material, with a dense and resistant crystalline structure.
Applications of chromium carbides
Thanks to their properties, chromium carbides are used in numerous sectors. In the automotive industry, they are used for surface hardening and in machine tools, where wear resistance is crucial. Additionally, the aerospace industry employs them for their exceptional mechanical properties.
Alloys and coatings: beyond carbides
Adding chromium to alloys, like stainless steel, greatly enhances the mechanical properties of materials. Chromium alloys are appreciated for their resistance to corrosion and high temperatures.
READ ALSO: Renewable energies: anti-wear coatings and sustainable solutions
Chromium coatings and PVD techniques
Beyond carbides, chromium is widely used in chromium coatings and PVD (Physical Vapor Deposition) techniques. These coating techniques improve the materials&#; resistance, making them ideal for demanding industrial applications.
Super-hard alloys and properties of carbides
When talking about super-hard alloys, chromium carbides are always in the spotlight. Their excellent mechanical properties combine strength and hardness, making them ideal for various applications.
READ ALSO: The importance of anti-wear coatings for mechanical parts
Comparison between chromium carbides and other anti-wear materials
Chromium carbides are among the most appreciated materials for anti-wear coatings, thanks to their distinctive properties. In terms of benefits, they offer exceptional wear resistance, especially when compared with traditional coatings such as hard nickel or aluminum oxide.
Their intrinsic hardness and the ability to bond strongly to metal bases make them ideal for high-stress applications, such as industrial machine components or construction equipment. Moreover, their resistance to corrosion and high temperatures makes them particularly useful in hostile environments and high-temperature applications.
On the other hand, the disadvantages of chromium carbides include a higher cost compared to some traditional anti-wear materials and the need for specialized equipment for their deposition. Additionally, due to their extreme hardness, they can be challenging to work or shape after deposition.
Nevertheless, when it comes to performance and longevity, chromium carbides often outperform other materials in anti-wear coatings, making them a preferred choice in many industrial applications.
Why turn to Paganoni specialized in chromium carbides coating?
Nel panorama industriale, i carburi di cromo e le loro applicazioni correlate giocano un ruolo cruciale. La loro versatilità, resistenza e durata li rendono ideali per svariate applicazioni. e quando si tratta di ottenere il meglio da questi materiali, rivolgersi ad un esperto come paganoni può fare la differenza.
Noi di Paganoni ci occupiamo di rivestimenti anti usura e i carburi di cromo sono essenziali per la riuscita del nostro lavoro.
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