Heavy Metals, their Salts, and other Compounds A Quick Reference Guide from AIC and the Health & Safety Committee A Special Insert By Cheryl Podsiki
Introduction trace element and beryllium, a light is an essential trace element  and its but very toxic metal . All metals are compounds, including soluble chro- The term heavy metal is a loosely characterized by their excellent abil- mium salts, are considered to be of used term generally accepted to mean ity to conduct heat and electricity (the low toxicity and are thought to present dense metals of relatively high atomic metalloids being semi-conductors), and few industrial hazards . Hexavalent mass, with a specific gravity of 4 or are malleable, ductile, hard, and shiny, chromium, Cr (VI), however, is highly above. Although there are several the exception being mercury which is toxic  and its compounds, includ- other definitions of the term there is liquid at room temperature. ing chromic acid and chromates, are no specific set of elements that would One of the most significant fac- potential carcinogens . imply any common set of properties tors about metals is their residual Posted on the AIC website, the such as high toxicity or high atomic persistence over time. Metallic com- “Chart of Heavy Metals, their Salts, weight . The heavy metals group pounds such as oxides, sulfides, chlo- and other Compounds” provides a includes transition metals, some met- rides, carbonates, nitrates, and other quick reference to the 35 elements alloids (elements that exhibit both salts are formed when positively and some of their compounds classi- metal and non-metal properties), some charged metals called cations react with fied and regulated by OSHA as heavy lanthanides and actinides, and often negatively charged elements called metals . Additional compounds includes reference to certain light anions in ionic or covalent bonds. often encountered in conservation are and trace metals with an inference to The resulting metallic compounds also listed. The guide is not definitive toxicity. An example of the ambigu- can result in very different proper- or all-inclusive; it is meant to be used ity of the term heavy metal is that of ties of solubility and toxicity . For in conjunction with other resources. molybdenum, a heavy but essential example, trivalent chromium, Cr (III), Complete information about each of AMERICAN INSTITUTE FOR CONSERVATION OF HISTORIC AND ARTISTIC WORKS • 1156 15TH STREET NW • SUITE 320 • WASHINGTON, DC 20005 • (202) 452-9545 • FAX (202) 452-9328 • WWW.AIC-FAIC.ORG their properties, toxicity, and specific tive to semi-quantitative. Some tests easily be used in storage rooms and compound or additional occupational are available in pre-packaged test kits. exhibition cases, as well as on-site for exposure levels can be found in MSDS Spot tests can be destructive or non- field archaeology. sheets, OSHA and NIOSH publica- destructive to the object or surface Inductively Coupled Plasma tions, and other health and regula- being tested depending on the method Spectroscopy (ICP) - Conducts mul- tory governing agencies found on the used. They all involve chemical reac- tiple elemental analyses using a tiny Internet and listed at the end of this tions and need to be conducted in a sample that must be dissolved for the guide. All health and safe handling safe controlled environment whether analysis (a destructive technique). Laser guidelines and hazardous waste disposal in the laboratory or in the field by Ablation-Inductively Coupled Plasma- should be followed as outlined by the trained personnel. Proper waste dispos- Mass Spectrometry (La-ICP-MS) various governing bodies; appropriate al guidelines for hazardous waste gen- models have the capability to analyze personal protective equipment (PPE) erated from the test procedure should certain whole objects. The instru- should be used as described in OSHA be followed [7, 8]. ment yields highly accurate quantita- regulations with particular attention tive results for low levels of elements. paid to the use of respirators. It is an excellent tool to crosscheck Analytical Instruments semi-quantitative to quantitative results Hand-held X-ray Florescence of the hand-held XRF . ICP is a Detection Methods Spectrometry (XRF) - A surface tech- laboratory procedure that must be The appropriate testing method nique, the XRF analyzer conducts conducted by qualified personnel [7, to use for the detection of a spe- multiple elemental analyses and is 10, 11]. cific heavy metal will depend on the considered to be non-destructive to Atomic Absorption Spectroscopy answers to some key questions: the object. It can be used with swabs, (AAS) - Analyzes one element at a • What do you want to know and wipes, or in direct contact with the time using a tiny sample that must be why? surface. The instrument yields quanti- dissolved for the analysis (a destruc- • What is the material type of the tative results for modern metal alloys tive technique). The instrument object to be tested? or soils based on approved NIST yields highly accurate quantitative • Can a sample be taken or must the industrial standards and calibrations results for low levels of elements. test be non-destructive? for which the instruments were made. The use of High Performance Liquid Regardless of the testing method, Results on archaeological metals and Chromatography (HPLC) in conjunc- test results on homogeneous samples glass substrates range from qualita- tion with AAS analysis (used as the are usually indicative of the entire tive to quantitative; results on organic detector) can provide speciation of object, however, results on heteroge- substrates are presently qualitative, but the sample [12.] AAS is a laboratory neous samples (such as organic sub- with appropriate reference materials, procedure that must be conducted by strates) are indicative of the specific instrument calibrations may be able qualified personnel [7, 10, 11]. test site/sample only. Quantitative to offer semi-quantitative ranges. The Spark Emission Spectroscopy - A results are relevant only for the sample instrument is easy to use but spectrum destructive technique that tests mostly or site tested. and data are complicated to interpret, solids and is good for bulk constituents especially on organic substrates because . the data alone cannot be relied on for Wet Chemical Techniques - Spot Tests accurate results and spectrum must Samples must be dissolved (destructive Spot test procedures are relatively be interpreted. Trained personnel are techniques). Wide variety of possible reliable indicators of the presence of necessary for application and accurate techniques, titrations, ion-specific residual surface chemicals. They can interpretation. The hand-held XRF electrodes, etc; may be very useful provide results ranging from qualita- is an excellent screening tool and can depending on the analyte and levels to be analyzed . List of Acronyms Acronyms used in the chart and references: Ion Chromatography - Low lev- CAS: Chemical Abstract Service (chemical For a comprehensive lists of acronyms, els (range of 0.1 ppm) of multiple ions health agencies and governing bodies refer to registry number) MSDS: Material Safety Data Sheets can be determined giving quantitative the following websites: PEL: Permissible exposure limit - OSHA regu- results. The samples must be dissolved ACGIH: American Conference of Govern- lated concentrations mental Industrial Hygienists, www.acgih. making it a destructive technique [7, TLV: Threshold limit value - ACGIH sug- 10]. org gested concentration guidelines CDC: Center for Disease Control and Preven- TWA: Time-weighted average - NIOSH rec- tion, www.cdc.gov ommended exposure limits (RELs) DHHS: U.S. Department of Health and Hu- ppm: parts per million (conversion factors: Health and Safety man Services, www.os.dhhs.gov parts of vapor or gas per million parts of EPA: U. S. Environmental Protection Agency, Unlike industrial workers who contaminated air by volume at 25ºC and 1 are more likely to encounter higher www.epa.gov atmosphere) OSHA: Occupational Safety and Health Ad- mg/m3: milligrams per cubic meter (conver- doses of potentially hazardous materi- ministration, www.osha.gov sion factors: milligrams of vapor or gas per als resulting in acute exposure , NIOSH: National Institute for Occupational cubic meter of contaminated air at 25ºC museum workers are more likely Safety and Health, www.cdc.gov/niosh and 1 atmosphere) to be exposed to low-level doses of
2 aic news, November 2008 heavy metals over an extended period tions listed for the product. Dispose returning it to the store room . All of time, resulting in chronic health of containers and unused contents in pertinent PPE should be used through- problems. Heavy metal exposure in accordance with federal, state and local out the process. the environment along with that from requirements . Laboratory safety *The specific time interval is unknown museum collections and buildings is protocol should be followed. MSDS as it relates directly to the level of airflow and of particular concern to museum pro- documents must be on the premises other factors in the room. Air quality tests can fessionals involved in emergency and in the lab for each substance present. be conducted to determine the time frame using disaster rescue and recovery efforts. Unless a substance is known to not a Jerome 431-X Mercury Vapor Analyzer and Health and safe handling guidelines for be hazardous, it should be treated as a Lumex RA-915+ Multifunctional Mercury specific metals and their compounds though it was hazardous. analyzer . have been developed by national and Documentation- All test results, international governing health and suspect hazards and known archival environmental agencies and are read- information should be documented A Specific Note About ily available in electronic form and (written, photo, analytical test results) Arsenic as Arsine in numerous hardcopy publications. and filed appropriately (electronically/ Institutions in the U.S. are required to hard copy) for easy access by person- Possible exposure to arsine for follow OSHA health and safety regula- nel who handle the material. All tested conservators, collection managers and tions and dispense all known informa- objects, shelves, drawers, and stor- other museum workers is normally tion about existing hazards to person- age room doors should be identified confined to controlled chemical reac- nel and handlers of the materials under as having been tested with clear and tions such as in the arsenic spot test. In OSHA’s 1986 Hazard Communication concise hazard identification labels or view of the recent natural disasters that Standard providing employees with the tags, and for an individual item, both have been occurring, museum workers right to know . the object and the container (polyeth- and disaster recovery teams should be Personal Protective Equipment ylene bag, box) and/or isolated shelf or aware that arsine gases can also form as (PPE) - Consult OSHA regulations, drawer should be labeled. a result of the natural (and complex) NIOSH recommendations, and MSDS biomethylation process undertaken sheets as well as other resources per- by certain organometallic micro- taining to specific PPE required for use A Specific Note organisms in the environment . with certain hazardous materials and About Mercury Although highly unlikely to be found standard lab procedures. Nitrile gloves, in environmentally climate-controlled lab coats, booties, hair nets, protective Inhalation of mercury vapor is institutions, it is possible that under suits, dust masks and respirators are of particular concern if working in an certain moisture/ high humidity con- standard PPE for use in conservation enclosed, not well-ventilated room. ditions where mold may form, these laboratories. Respirator use is governed Therefore, it is suggested that person- micro-organisms could be present and by OSHA . Those who need/ nel not work in certain storage areas this increases the potential of arsine choose to use respirators must obtain or the confines of an exhibit case. To being present [18, 19]. High levels of medical clearance, receive use training retrieve an object suspected or known methylated arsenic compounds have and have their respirator individually to be fabricated or contaminated with been found in confined spaces in fit tested by authorized testers prior to a mercury compound, it is suggested greenhouses and in relation to arsine use. Members of the Health & Safety that the drawer or cabinet where the poisoning incidents involving the pig- Committee provide training and fit object is housed be opened and that ment, Paris Green (copper acetoarse- testing at the annual AIC meetings. All individuals immediately leave the nite), in wall paper [17, 20]. Arsine has respirators must be NIOSH approved room for a period of time* without a subtle garlic odor associated with its for the specific type of mask, filter, or breathing in the air directly in front of presence. cartridge needed [14, 15]. or above the housing unit. This will Handling and Storage - In gen- allow any mercury vapor that may An expanded version of the Heavy eral, most objects containing hazardous have built up in the enclosed drawer Metals Reference Guide is available materials should be kept in a tightly or cabinet to be released into the online through the AIC Health & closed container, stored in a cool, ambient air. Once it is safe to return Safety Committee’s webpage. This dry, ventilated area, isolated from any to the room, remove the object to a document includes a chart with an source of heat or ignition and in an well-ventilated area rather than work extensive listing of OSHA regulated area where it will be protected against in the store room if at all possible. heavy metals, their salts, and other physical damage. Do not use or store The same precaution should be taken compounds. This handy reference hazardous materials on porous work when opening an enclosed container guide details the physical description, surfaces (wood, unsealed concrete, to retrieve an object: e.g. open/unseal use, occupational exposure limits, and etc.). Follow strict hygiene practices. a bagged object in a fume hood or chemical formulae of over one hun- Containers may be hazardous when well-ventilated room, leave the area dred compounds. Visit empty since they can retain product and return after a period of time* to www.aic-faic.org to download a copy residues (dust, solids, vapors, liquid); continue work. When work is com- for your lab today. observe all warnings and precau- pleted then re-seal the container before
3 aic news, November 2008 References: 12/2  INCHEM, IPCS International Program Mercury in museum collections, 1/7 Note: this section is applicable to the printed text and in Chemical Safety. Environmental Health Care of alum, vegetable, and mineral tanned the on-line chart. Criteria 18: Arsenic. 1-144. http://www. leather, 8/2 inchem.org/documents/ehc/ehc/ehc018. Care of encased photographic images, 16/1  OSHA regulated heavy metals: http://www. htm osha.gov/SLTC/metalsheavy/  Hawks, C. and K. Makos. 2001. Hidden regulated.html  Hirner, A.V. et al. 1998. Metal(loid) or- hazards: the dark side of collections. CIPP ganic compounds in geothermal gases and Post Prints. Health and safety session. 2001  Wade. L.G., Jr. 1991. Organic Chemistry. water. Organic Geochemistry. Vol. 29. No. AIC Annual Meeting. Dallas, Texas. June Second edition. Prentice Hall: Englewood 57. 2001. 5-51. Cliffs, New Jersey. 1765-1778. Great Britain: Elsvier Science, Ltd.  Brückle, I., C. Tahk, C. Baker. 1996. Alka-  Chemie.De Information Service; Encyclope-  Reimer, K. 2002. Director of Environmen- line solutions: simple chemistry, preparation dia of chemistry, analytics and pharmaceu- tal Sciences Group, Royal Military College. and uses. CNS 632: Technology and Conser- tics: http://www.chemie.de/lexikon/e/ Kingston, Ontario, Canada. Personal com- vation of Works of Art on paper II; Alkaline Heavy_metals/ munication. Solutions, 1/12. Class course. Buffalo State University. Art Conservation Program.  Dartmouth Toxic Metal Research: http://  Kelman, L. 1999. Considerations for the www.dartmouth.edu/~toxmetal/ conservation of fur-bearing mammal collec-  Burgess, H., S. Duffy and S. Tse. 1991. TX.shtml tions. SSCR Journal. February 1999 Vol.10. Investigation of the effect of alkali on cellu- No.1. 10-14. losic fibers; part 1: rag and processed wood  McCann, M. 1992. Artist beware. New York: pulp paper. Paper and textiles: the common The Lions Press.  NIOSH pocket guide to Chemical Hazards. ground. Preprints of conference held at The September 2005. http://www.cdc.gov/ Burrell Collection. Glasgow. September 19-  Goyer, R A. and T.W. Clarkson. 2001. niosh/npg/default.html 20, 1991. SSCR. 29-47. Toxic effects of metals. Casarett and Doull’s Toxicology: the basic science of poisons. Ed.  Immediately Dangerous to Life and Health  Paper Conservation Catalogue. BPG. AIC C.D. Klaassen. 839-848. Concentrations (IDLHC). Oct. 2003. 2nd edition. 1985. Alkalization or deacidifi- NIOSH Pocket guide to chemical hazards and cation processes. ARTC 831. Paper stream.  Odegaard, Nancy and Alice Sadongei other databases. CD format. DHHS (NIOSH) Queen’s University Master of Arts Conser- and Associates. 2005. Old poisons, new Publication No. 2004-103. vation program. problems; a museum resource for managing cultural materials. Walnut Creek, CA: Alta  International Chemical Safety Cards  Konefes, J. L. and M. K. McGee. 1996. Mira Press. (ICSC). March 2008. http://www.cdc.gov/ Old cemeteries, arsenic, and health safety. niosh/ipcs/icstart.html Cultural Resource Management (CRM). Foren-  Hawks, C., K. Makos, D. Bell, G. E. Bur- sic archeology: a humanistic science. 19-10. roughs, and P.F. Wambach. 2004. An inex-  http://www.periodictable.com/ CRM online: http://crm.cr.nps.gov/results. pensive method to test for mercury vapor in Elements/033/index.wt.html cfm herbarium cabinets. TAXON.  http://www.fluoridealert.org/pesticides/  Gettens, R.J. and G. Stout. 1966. Painting  Laure Dussubieux, 2008. Analytical scientist/ sodium.aluminum.fluosilica.htm materials: a short encyclopedia. New York: Do- Manager of LA-ICP-MS Lab at The Field ver Publications, Inc. Museum, Chicago. Personal communica-  http://chemistry.about.com/library/ tion. weekly/blcommon.html  Goldberg, Lisa. 1996. A history of pest con- trol measures in the anthropology collec-  Skoog, D.A., F.J. Holler, and T.A. Nie-  http://msds.chem.ox.ac.uk/newcas.html tions, National museum of natural history, man. 1998. Principles of instrumental analysis. Smithsonian Institution. JAIC. 35 (1996): Philadelphia: Saunder College Publishing.  http://www.cameochemiclas.noaa.gov 23-43.
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