Volume 46 Number 2
Acrylonitriles -- Settling on an Industry Standard
At the Water Quality Association’s (WQA) Mid-Year Leadership Conference in Chicago last October, a presenter raised the issue of the emerging contaminant, acrylonitrile, and the need for growing awareness among WQA members. In contrast to most drinking water contaminants, removal of acrylonitrile from contaminated source water concerns largely the manufacturers of drinking water treatment units (DWTU). In addition, they are also concerned with not adding more of the contaminant to treated water because of any materials used in the design of these units.
Acrylonitrile is a colorless liquid with a strong onion- or garlic-like odor. Ranking among the 50 highest-volume chemicals produced in 1999, 117 facilities released over 5.4 million pounds into the environment with 17.9 percent going into underground injection wells. Once in the environment, however, the chemical--especially when contacted with ultraviolet (UV) light--tends to break down rapidly. It has a half-life of five to 50 hours under such conditions.
A manufactured chemical, acrylonitrile is used to make plastics, synthetic rubber, elastomers, acrylic fibers and resins, i.e., acrylonitrile-butadiene-styrene (ABS). Since ABS materials are resistant to rust and corrosion and are relatively lightweight, they’re an attractive resin for pipe and housing construction and are commonly used in point-of-use DWTUs.
In addition to these acute effects, chronic exposures may also lead to a higher incidence of cancer. The U.S. Environmental Protection Agency (USEPA) has classified acrylonitrile as a Group B1 contaminant meaning that it’s a probable human carcinogen (cancer-causing agent). Although human data are inconclusive, animal studies have shown that acrylonitrile causes cancers of the stomach, brain and mammary glands, among others. Birth defects have been seen in animals and reproductive disorders have been realized through three generations in laboratory tests.
Exposure risks are difficult to extrapolate to humans, where personal characteristics can vary individual risks substantially. Children, however, appear to be much more sensitive to acrylonitriles since deaths have occurred in children in acute exposure compared to only minor symptoms in adults.
Waterborne exposure routes
In addition to water, the general population may be exposed to acrylonitriles in plastic products. Regulatory safeguards are therefore in place to prevent consumption of acrylonitriles through consumer product usage. Many, if not most, DWTUs utilize ABS components that contact water during the course of water treatment. Typically, the concentration of acrylonitrile in ABS copolymers is about 30 to 50 parts per million (ppm). The amount suspected of leaching from the plastic product to the water supply is considered to be extremely low.
Testing protocols in DWTU standards differ from that of Standard 61 (see www.nsf.org/newsletters/regworld 01-2/ for a description of specific protocols), whereby many of the Standard 61 sections require an extended conditioning period; however, the overall goal is the same. In general, the test standards are aimed at ensuring materials in contact with drinking water don’t impart levels of extractable contaminants exceeding maximum drinking water levels (MDWLs) specified in the standard. These contaminants may be regulated or unregulated. Food-grade (FDA Title 21 CFR-compliant) ABS has been tested and certified extensively by NSF, WQA and UL as meeting DWTU standards.
Proposals & rebuttals
In January 2002, a balloted action was presented before the NSF Council of Public Health Consultants proposing, in part, a revision of the DWTU standards. These revisions would have changed the present extraction test level of 5 ppb (currently, an advisory concentration) to 0.6 ppb (a mandatory MDWL). Such a revision would have placed a marked burden on the DWTU industry where previous detection limits reportedly ranged between 1.0 ppb and 5.0 ppb--thus requiring re-testing of units containing ABS plastic to ensure compliance with a new, lower level.
Following the proposed MDWL of 0.6 ppb in the DWTU acrylonitrile standard, representatives from the domestic drinking water treatment equipment industry voiced the need for further discussions and review. In particular, discussions were requested regarding the technological and economical feasibility of current testing protocols used to evaluate DWTUs. The proposed requirement of 0.6 ppb was determined on the basis of NSF/ANSI Standard 61 safety levels but did not consider the variations in test protocols used in Standard 61 vs. DWTU testing procedures.
2. ATSDR, “Agency for toxic substances and disease registry,” Atlanta, Ga., ToxFAQs for Acrylonitrile, www.astr.cdc.gov/tfacts125. html, July 1999.
3. Acrylonitrile, CAS #107-13-1, from “Second Annual Report on Carcinogens,” Environmental Health Perspectives Online, National Institutes of Health, Washington, D.C.: http://ehp.niehs.nih.gov/roc/tenth/profiles/s004acry.pdfhttp://ehp.niehs.nih.gov/roc/tenth/profiles/s004acry.pdf
4. ATSDR, “Toxicological profile for acrylonitrile (final report),” Atlanta, Ga., pp. 140, Accession #PB91-180489, 1990.
5. USEPA, “EPA Technology transfer network air toxics website,” Acrylonitrile #107-13-1, www.epa.gov/ttn/atw/hlthef/acryloni.html , updated Feb 2003.
6. USEPA, “2002 Edition of the Drinking Water Standards and Health Advisories,” Office of Water, USEPA, Washington, D.C, EPA 822-R-02-038, www.epa.gov/waterscience/drinking/standards/dwstandards.pdf
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EXTRA: Acrylonitrile* National Institute for Occupational Safety and Health, “Current Intelligence Bulletin 18: Acrylonitrile,” CDC website: www.cdc.gov/niosh/78127_18.html * National Safety Council, “Acrylonitrile Chemical Back-grounder”: www.nsc.org/library/chemical/acryloni.htm * Chemical Economics Handbook, “CEH Report on Acrylonitrile,” SRI Consulting: http://ceh.sric.sri.com/Public/Reports/607.5000/ * Assessment Report-Acrylonitrile, Environment Canada, CEPA Registry: www.ec.gc.ca/substances/ese/eng/psap/final/acrylonitrile.cfm