National Academies Press: OpenBook

Public Health Consequences of E-Cigarettes (2018)

Chapter: 14 Injuries and Poisonings

« Previous: 13 Developmental and Reproductive Effects
Suggested Citation:"14 Injuries and Poisonings." National Academies of Sciences, Engineering, and Medicine. 2018. Public Health Consequences of E-Cigarettes. Washington, DC: The National Academies Press. doi: 10.17226/24952.
×

14

Injuries and Poisonings

There is no question that sources of morbidity and mortality from e-cigarettes are the injuries related to malfunctioning of the devices, leading to burns and projectile injuries, and injuries related to intentional or unintentional consumption of e-liquids. There are no epidemiological studies of these events, but the literature does contain numerous case reports, case series, and reports from passive surveillance systems, such as poison control centers. The committee briefly reviews this evidence. The committee notes that in recognition of these injuries, Congress and the Food and Drug Administration (FDA) have taken action. In 2016, Congress directed the Consumer Product Safety Commission to require special packaging (similar to child-resistant packaging) for e-liquid bottles that contain nicotine.1 FDA’s Center for Tobacco Products recently held a public workshop to discuss battery safety (HHS, 2017). Finally, in recognition of the risks, FDA’s recently released comprehensive nicotine strategy includes provisions for setting product standards “to protect against known public health risks such as electronic nicotine delivery systems (ENDS) battery issues” and for “concerns about children’s exposure to liquid nicotine” (HHS, 2017).

___________________

1 Child Nicotine Poisoning Prevention Act of 2015, Public Law 114-116 § 142, 114th Cong. (September 29, 2017).

Suggested Citation:"14 Injuries and Poisonings." National Academies of Sciences, Engineering, and Medicine. 2018. Public Health Consequences of E-Cigarettes. Washington, DC: The National Academies Press. doi: 10.17226/24952.
×

BURNS AND EXPLOSIONS

Most of the information regarding the malfunction of e-cigarettes and injuries comes from case reports, case series, and retrospective reviews of burn center reports. No prospective observational studies have been identified. Although these events are infrequent and the true rate is not known, when they do occur they have the potential to cause great harm. Serious burns from exploding e-cigarette batteries have been reported in the literature. Overheating and explosions of lithium ion batteries in e-cigarettes are most frequently the cause of burns in e-cigarette users. The quality of the components and design of the device, including user modifications, may influence the likelihood of malfunction and explosions in e-cigarettes. The committee reviewed 46 case reports published in the literature as solo case reports or case series documenting burns to the face, chest, abdomen, genitalia, and thigh, with burns to the thigh area most frequently reported. The majority (n = 25) of the cases of burns to the thigh are from devices stored in pants pockets (Bauman et al., 2016; Bohr et al., 2016; Colaianni et al., 2016; Herlin et al., 2016; Jiwani et al., 2017; Kumetz et al., 2016; Nicoll et al., 2016; Serror et al., 2017; Sheckter et al., 2016; Treitl et al., 2016; Walsh et al., 2016). Some explosions are documented to occur when the device could have come into content with metals, such as coins and keys, in the pocket.

There have also been reports of injuries caused by projectiles following an e-cigarette explosion. Vaught and colleagues (2017) reported facial trauma from such an explosion. Another case reported that an 18-year-old suffered oral trauma and tooth avulsion following an e-cigarette explosion while using the device (Rogér et al., 2016). Paley and colleagues (2016) reported two cases of severe corneal injuries, in addition to other facial injuries that occurred in an adult and adolescent when their e-cigarettes exploded, resulting in decreased visual acuity.

Several groups have published summaries of reported explosions causing harm, based on reports from general hospitals or burn treatment centers (Arnaout et al., 2017; Brownson et al., 2016; Hassan et al., 2016; Rudy and Durmowicz, 2016). For example, Ramirez and colleagues (2017) found that 29 people were referred between February 2015 and July 2016 to three regional burn treatment centers in California for burn-related injuries from e-cigarettes. In addition, Arnaout and colleagues (2017) reported on 12 people who were treated for e-cigarette injuries in two burn centers in the United Kingdom, between October 2015 and July 2016. In their study, the thigh region was the most common area for a burn. Another study from California found that 25 patients were treated for burns caused by e-cigarettes at a regional burn center, between November 2015 and March 2017 (Toy et al., 2017). The majority of patients were male and most injuries resulted from the e-cigarette device exploding in

Suggested Citation:"14 Injuries and Poisonings." National Academies of Sciences, Engineering, and Medicine. 2018. Public Health Consequences of E-Cigarettes. Washington, DC: The National Academies Press. doi: 10.17226/24952.
×

a pocket, with thigh and genital areas being most commonly affected. Malfunctions of the lithium battery in the e-cigarettes have been blamed for many of these injuries, but Serror and colleagues (2017) reported on a patient who had a full-thickness thigh burn due to overheating of a resistor component of the e-cigarette, in the absence of the device catching fire or exploding.

INTENTIONAL AND UNINTENTIONAL EXPOSURE TO E-LIQUID

Ingestion of nicotine-containing e-cigarette solutions can result in serious health effects, including death, due to nicotine toxicity. Many of the commercially available e-cigarette solutions contain high concentrations of nicotine. The committee identified 19 case reports (documented in 16 publications) in the literature of poisonings from exposure to e-liquid via oral or dermal routes. Twelve of these incidents are reported as intentional (sometimes associated with a suicide note) (Bartschat et al., 2015; Chen et al., 2015; Christensen et al., 2013; Eberlein et al., 2014; Garat et al., 2016; Lam et al., 2016; Schipper et al., 2014; Sommerfeld et al., 2016; Thornton et al., 2014; You et al., 2016), and six as unintentional (Eggleston et al., 2016; Gill et al., 2015; Gupta et al., 2014; Jamison and Lockington, 2016; Noble et al., 2016; Seo et al., 2016). Fatalities have been reported (Eggleston et al., 2016; Thornton et al., 2014; You et al., 2016). The medical consequences of the non-fatal cases include vomiting, lactic acidosis (Garat et al., 2016), and other outcomes. Several of these unintentional cases involved young children who apparently accessed e-liquid vials in the household (Eggleston et al., 2016; Gill et al., 2015; Gupta et al., 2014).

Further evidence of the consequence of ingestion of e-liquid is found in reports from poison control centers and other passive surveillance systems (Anonymous, 2015; Cantrell and Clark, 2014; Chatham-Stephens et al., 2014, 2016; De La Oliva Urieta and Conejo Menor, 2014; Forrester, 2015; Kamboj et al., 2016; Lovecchio and Zoph, 2015; Ordonez et al., 2015; Thomas et al., 2014; Vakkalanka et al., 2014; Valentine et al., 2016; Weiss et al., 2016). For example, between January 2010 and June 2014, poison control centers in Texas received 203 reports of ingestion by children age 5 or younger (Forrester, 2015). Between January 2013 and April 2014, 64 cases of e-liquid exposure were reported to Spain’s poison centers, 28 percent of which were in children younger than 2 years of age (De La Oliva Urieta and Conejo Menor, 2014). Between September 2010 and February 2014, poison control centers in the United States recorded 2,405 calls regarding e-cigarette exposures (Chatham-Stephens et al., 2014). Children age 5 and younger accounted for 51 percent of those calls. In the United States, the number of calls to poison centers for e-cigarette exposures increased 1,492.9 percent between January 2012 and April 2015

Suggested Citation:"14 Injuries and Poisonings." National Academies of Sciences, Engineering, and Medicine. 2018. Public Health Consequences of E-Cigarettes. Washington, DC: The National Academies Press. doi: 10.17226/24952.
×

(Kamboj et al., 2016). E-cigarette exposures were also more likely to result in a health care admission and a more severe outcome than an exposure related to cigarettes.

Although the committee identified no epidemiological studies about injuries and poisonings, the type of evidence that supports other conclusions in this report, the committee viewed the case studies as sufficient basis for several conclusions.

Conclusion 14-1. There is conclusive evidence that e-cigarette devices can explode and cause burns and projectile injuries. Such risk is significantly increased when batteries are of poor quality, stored improperly, or modified by users.

Conclusion 14-2. There is conclusive evidence that intentional or accidental exposure to e-liquids (from drinking, eye contact, or dermal contact) can result in adverse health effects including but not limited to seizures, anoxic brain injury, vomiting, and lactic acidosis.

Conclusion 14-3. There is conclusive evidence that intentionally or unintentionally drinking or injecting e-liquids can be fatal.

REFERENCES

Anonymous. 2015. Electronic cigarettes: Poisoning in children. 2015. Prescrire International 24(156):21.

Arnaout, A., F. Dewi, and D. Nguyen. 2017. Re: Burn injuries from exploding electronic cigarette batteries: An emerging public health hazard. Journal of Plastic, Reconstructive & Aesthetic Surgery 70(7):981–982.

Bartschat, S., K. Mercer-Chalmers-Bender, J. Beike, M. A. Rothschild, and M. Jubner. 2015. Not only smoking is deadly: Fatal ingestion of e-juice—A case report. International Journal of Legal Medicine 129(3):481–486.

Bauman, Z. M., J. Roman, M. Singer, and G. A. Vercruysse. 2016. Canary in the coal mine—Initial reports of thermal injury secondary to electronic cigarettes. Burns 43(3):e38–e42.

Bohr, S., F. Almarzouqi, and N. Pallua. 2016. Extensive burn injury caused by fundamental electronic cigarette design flaw. Annals of Burns and Fire Disasters 29(3):231–233.

Brownson, E. G., C. M. Thompson, S. Goldsberry, H. J. Chong, J. B. Friedrich, T. N. Pham, S. Arbabi, G. J. Carrougher, and N. S. Gibran. 2016. Explosion injuries from e-cigarettes. New England Journal of Medicine 375(14):1400–1402.

Cantrell, F. L., and R. F. Clark. 2014. More on nicotine poisoning in infants. New England Journal of Medicine 371(9):880. https://doi.org/10.1056/NEJMc1407921 (accessed February 6, 2018).

Chatham-Stephens, K., R. Law, E. Taylor, P. Melstrom, R. Bunnell, B. Wang, B. Apelberg, and J. G. Schier. 2014. Notes from the field: Calls to poison centers for exposures to electronic cigarettes—United States, September 2010–February 2014. Morbidity and Mortality Weekly Report 63(13):292–293.

Suggested Citation:"14 Injuries and Poisonings." National Academies of Sciences, Engineering, and Medicine. 2018. Public Health Consequences of E-Cigarettes. Washington, DC: The National Academies Press. doi: 10.17226/24952.
×

Chatham-Stephens, K., R. Law, E. Taylor, S. Kieszak, P. Melstrom, R. Bunnell, B. Wang, H. Day, B. Apelberg, L. Cantrell, H. Foster, and J. G. Schier. 2016. Exposure calls to U.S. poison centers involving electronic cigarettes and conventional cigarettes—September 2010–December 2014. Journal of Medical Toxicology 12(4):350–357.

Chen, B. C., S. B. Bright, A. R. Trivedi, and M. Valento. 2015. Death following intentional ingestion of e-liquid. Clinical Toxicology 53(9):914–916.

Christensen, L. B., T. van’t Veen, and J. Bang. 2013. Three cases of attempted suicide by ingestion of nicotine liquid used in e-cigarettes [abstract]. Clinical Toxicology 51:290. https://doi.org/10.3345/kip.2016.59.12.490 (acceessed February 6, 2018).

Colaianni, C. A., L. F. Tapias, R. Cauley, R. Sheridan, J. T. Schulz, and J. Goverman. 2016. Injuries caused by explosion of electronic cigarette devices. Eplasty 16:ic9.

De La Oliva Urieta, S., and J. L. Conejo Menor. 2014. Exposures to electronic cigarettes: Calls to the poison center in Spain. Revista Espanola de Medicina Legal 40(4):146–149.

Eberlein, C. K., H. Frieling, T. Kohnlein, T. Hillemacher, and S. Bleich. 2014. Suicide attempt by poisoning using nicotine liquid for use in electronic cigarettes. American Journal of Psychiatry 171(8):891. https://doi.org/10.1176/appi.ajp.2014.14030277 (accessed February 6, 2018).

Eggleston, W., N. Nacca, C. M. Stork, and J. M. Marraffa. 2016. Pediatric death after unintentional exposure to liquid nicotine for an electronic cigarette. Clinical Toxicology 54(9):890–891.

Forrester, M. B. 2015. Pediatric exposures to electronic cigarettes reported to Texas poison centers. Journal of Emergency Medicine 49(2):136–142.

Garat, A., P. Nisse, M. Kauv, M. Mathieu-Nolf, D. Allorge, and D. Mathieu. 2016. Lactic acidosis due to voluntary e-liquid ingestion. Toxicologie Analytique et Clinique 28(4):329–332.

Gill, N., G. Sangha, N. Poonai, and R. Lim. 2015. E-cigarette liquid nicotine ingestion in a child: Case report and discussion. Canadian Journal of Emergency Medicine 17(6):699–703.

Gupta, S., A. Gandhi, and R. Manikonda. 2014. Accidental nicotine liquid ingestion: Emerging paediatric problem. Archives of Disease in Childhood 99(12):1149. http://doi.org/10.1136/archdischild-2014-306750 (accessed February 6, 2018).

Hassan, S., M. U. Anwar, P. Muthayya, and S. Jivan. 2016. Burn injuries from exploding electronic cigarette batteries: An emerging public health hazard. Journal of Plastic, Reconstructive & Aesthetic Surgery 69(12):1716–1718.

Herlin, C., F. Bekara, N. Bertheuil, P. Frobert, R. Carloni, and B. Chaput. 2016. Deep bums caused by electronic vaping devices explosion. Burns 42(8):1875–1877.

HHS (U.S. Department of Health and Human Services). 2017. Battery safety concerns in electronic nicotine delivery systems (ENDS) public workshop—April 2017. https://www.fda.gov/tobaccoproducts/newsevents/ucm535185.htm (accessed October 4, 2017).

Jamison, A., and D. Lockington. 2016. Ocular chemical injury secondary to electronic cigarette liquid misuse. JAMA Ophthalmology 134(12):1443. https://doi.org/10.1001/jamaophthalmol.2016.3651 (accessed February 6, 2018).

Jiwani, A. Z., J. F. Williams, J. A. Rizzo, K. K. Chung, B. T. King, and L. C. Cancio. 2017. Thermal injury patterns associated with electronic cigarettes. International Journal of Burns and Trauma (1):1–5.

Kamboj, A., H. A. Spiller, M. J. Casavant, T. Chounthirath, and G. A. Smith. 2016. Pediatric exposure to e-cigarettes, nicotine, and tobacco products in the United States. Pediatrics 137(6):e20160041. https://doi.org/10.1542/peds.2016-0041 (accessed February 6, 2018).

Kumetz, E. A., N. D. Hurst, R. J. Cudnik, and S. L. Rudinsky. 2016. Electronic cigarette explosion injuries. American Journal of Emergency Medicine 34(11):2252.e1–2252.e3.

Lam, C. N., N. I. Goldenson, E. Burner, and J. B. Unger. 2016. Cultural buffering as a protective factor against electronic cigarette use among Hispanic emergency department patients. Addictive Behaviors 63:155–160.

Suggested Citation:"14 Injuries and Poisonings." National Academies of Sciences, Engineering, and Medicine. 2018. Public Health Consequences of E-Cigarettes. Washington, DC: The National Academies Press. doi: 10.17226/24952.
×

Lovecchio, F., and O. Zoph. 2015. Incidence of electronic cigarette exposures in children skyrockets in Arizona. American Journal of Emergency Medicine 33(6):834–835.

Nicoll, K. J., A. M. Rose, M. A. A. Khan, O. Quaba, and A. G. Lowrie. 2016. Thigh burns from exploding e-cigarette lithium ion batteries: First case series. Burns 42(4):e42–e46.

Noble, M. J., B. Longstreet, R. G. Hendrickson, and R. Gerona. 2016. Unintentional pediatric ingestion of electronic cigarette nicotine refill liquid necessitating intubation. Annals of Emergency Medicine 69(1):94–97.

Ordonez, J. E., K. C. Kleinschmidt, and M. B. Forrester. 2015. Electronic cigarette exposures reported to Texas poison centers. Nicotine & Tobacco Research 17(2):209–211.

Paley, G. L., E. Echalier, T. W. Eck, A. R. Hong, A. V. Farooq, D. G. Gregory, and A. J. Lubniewski. 2016. Corneoscleral laceration and ocular burns caused by electronic cigarette explosions. Cornea 35(7):1015–1018.

Ramirez, J. I., C. A. Ridgway, J. G. Lee, B. M. Potenza, S. Sen, T. L. Palmieri, D. G. Greenhalgh, and P. Maguina. 2017. The unrecognized epidemic of electronic cigarette burns. Journal of Burn Care & Research 38(4):220–224.

Rogér, J. M., M. Abayon, S. Elad, and A. Kolokythas. 2016. Oral trauma and tooth avulsion following explosion of e-cigarette. Journal of Oral and Maxillofacial Surgery 74(6):1181–1185.

Rudy, S. F., and E. L. Durmowicz. 2016. Electronic nicotine delivery systems: Overheating, fires and explosions. Tobacco Control 26:10–18.

Schipper, E. M., L. C. de Graaff, B. C. Koch, Z. Brkic, E. B. Wilms, J. Alsma, and S. C. Schuit. 2014. A new challenge: Suicide attempt using nicotine fillings for electronic cigarettes. British Journal of Clinical Pharmacology 78(6):1469–1471.

Seo, A. D., D. C. Kim, H. J. Yu, and M. J. Kang. 2016. Accidental ingestion of e-cigarette liquid nicotine in a 15-month-old child: An infant mortality case of nicotine intoxication. Korean Journal of Pediatrics 59(12):490–493.

Serror, K., M. Chaouat, A. De Runz, M. Mimoun, and D. Boccara. 2017. Thigh deep burns caused by electronic vaping devices (e-cigarettes): A new mechanism. Burns 43(5):1133–1135.

Sheckter, C., A. Chattopadhyay, J. Paro, and Y. Karanas. 2016. Burns resulting from spontaneous combustion of electronic cigarettes: A case series. Burns Trauma 4:35. https://doi.org/10.1186/s41038-016-0061-9 (accessed February 6, 2018).

Sommerfeld, K., M. Lukasik-Glebocka, M. Kulza, A. Druzdz, P. Panienski, E. Florek, and B. Zielinska-Psuja. 2016. Intravenous and oral suicidal e-liquid poisonings with confirmed nicotine and cotinine concentrations. Forensic Science International 262:E15–E20.

Thomas, E., R. A. Spears, G. Alldridge, C. V. Krishna, J. P. Thompson, M. Eddleston, J. A. Vale, and S. H. L. Thomas. 2014. E-cigarette liquid refills—A safe beverage? Analysis of enquiries to the U.K. National Poisons Information Service from 2007 to 2013. Clinical Toxicology 52(4):338–339.

Thornton, S. L., L. Oller, and T. Sawyer. 2014. Fatal intravenous injection of electronic nicotine delivery system refilling solution. Journal of Medical Toxicology 10(2):202–204.

Toy, J., F. Dong, C. Lee, D. Zappa, T. Le, B. Archambeau, J. T. Culhane, and M. M. Neeki. 2017. Alarming increase in electronic nicotine delivery systems-related burn injuries: A serious unregulated public health issue. American Journal of Emergency Medicine 35(11):1781–1782.

Treitl, D., R. Solomon, D. L. Davare, R. Sanchez, and C. Kiffin. 2016. Full and partial thickness burns from spontaneous combustion of e-cigarette lithium-ion batteries with review of literature. Journal of Emergency Medicine 53(1):121–125.

Vakkalanka, J. P., L. S. Hardison, Jr., and C. P. Holstege. 2014. Epidemiological trends in electronic cigarette exposures reported to U.S. poison centers. Clinical Toxicology 52(5): 542–548.

Suggested Citation:"14 Injuries and Poisonings." National Academies of Sciences, Engineering, and Medicine. 2018. Public Health Consequences of E-Cigarettes. Washington, DC: The National Academies Press. doi: 10.17226/24952.
×

Valentine, N., E. McClelland, J. Bryant, and R. McMillen. 2016. Electronic cigarettes in Mississippi: Issues facing healthcare providers and policy makers. Journal of the Mississippi State Medical Association 57(6):181–189.

Vaught, B., J. Spellman, A. Shah, A. Stewart, and D. Mullin. 2017. Facial trauma caused by electronic cigarette explosion. Ear, Nose and Throat Journal 96(3):139–142.

Walsh, K., Z. Sheikh, K. Johal, and N. Khwaja. 2016. Rare case of accidental fire and burns caused by e-cigarette batteries. BMJ Case Reports. https://doi.org/10.1136/bcr-2015-212868 (accessed February 6, 2018).

Weiss, D., C. D. Tomasallo, J. G. Meiman, P. D. Creswell, P. C. Melstrom, D. D. Gummin, D. J. Patel, N. T. Michaud, H. A. Sebero, and H. A. Anderson. 2016. Electronic cigarette exposure: Calls to Wisconsin poison control centers, 2010-2015. Wisconsin Medical Journal 115(6):306–310.

You, G., J. Rhee, Y. Park, and S. Park. 2016. Determination of nicotine, cotinine and trans-3’hydroxycotinine using LC/MC/MS in forensic samples of a nicotine fatal case by oral ingestion of e-cigarette liquid. Journal of Forensic Sciences 61(4):1149–1154.

Suggested Citation:"14 Injuries and Poisonings." National Academies of Sciences, Engineering, and Medicine. 2018. Public Health Consequences of E-Cigarettes. Washington, DC: The National Academies Press. doi: 10.17226/24952.
×

This page intentionally left blank.

Suggested Citation:"14 Injuries and Poisonings." National Academies of Sciences, Engineering, and Medicine. 2018. Public Health Consequences of E-Cigarettes. Washington, DC: The National Academies Press. doi: 10.17226/24952.
×
Page 473
Suggested Citation:"14 Injuries and Poisonings." National Academies of Sciences, Engineering, and Medicine. 2018. Public Health Consequences of E-Cigarettes. Washington, DC: The National Academies Press. doi: 10.17226/24952.
×
Page 474
Suggested Citation:"14 Injuries and Poisonings." National Academies of Sciences, Engineering, and Medicine. 2018. Public Health Consequences of E-Cigarettes. Washington, DC: The National Academies Press. doi: 10.17226/24952.
×
Page 475
Suggested Citation:"14 Injuries and Poisonings." National Academies of Sciences, Engineering, and Medicine. 2018. Public Health Consequences of E-Cigarettes. Washington, DC: The National Academies Press. doi: 10.17226/24952.
×
Page 476
Suggested Citation:"14 Injuries and Poisonings." National Academies of Sciences, Engineering, and Medicine. 2018. Public Health Consequences of E-Cigarettes. Washington, DC: The National Academies Press. doi: 10.17226/24952.
×
Page 477
Suggested Citation:"14 Injuries and Poisonings." National Academies of Sciences, Engineering, and Medicine. 2018. Public Health Consequences of E-Cigarettes. Washington, DC: The National Academies Press. doi: 10.17226/24952.
×
Page 478
Suggested Citation:"14 Injuries and Poisonings." National Academies of Sciences, Engineering, and Medicine. 2018. Public Health Consequences of E-Cigarettes. Washington, DC: The National Academies Press. doi: 10.17226/24952.
×
Page 479
Suggested Citation:"14 Injuries and Poisonings." National Academies of Sciences, Engineering, and Medicine. 2018. Public Health Consequences of E-Cigarettes. Washington, DC: The National Academies Press. doi: 10.17226/24952.
×
Page 480
Next: 15 Research Needs: Effects of E-Cigarettes on Health »
Public Health Consequences of E-Cigarettes Get This Book
×
Buy Paperback | $120.00 Buy Ebook | $94.99
MyNAP members save 10% online.
Login or Register to save!
Download Free PDF

Millions of Americans use e-cigarettes. Despite their popularity, little is known about their health effects. Some suggest that e-cigarettes likely confer lower risk compared to combustible tobacco cigarettes, because they do not expose users to toxicants produced through combustion. Proponents of e-cigarette use also tout the potential benefits of e-cigarettes as devices that could help combustible tobacco cigarette smokers to quit and thereby reduce tobacco-related health risks. Others are concerned about the exposure to potentially toxic substances contained in e-cigarette emissions, especially in individuals who have never used tobacco products such as youth and young adults. Given their relatively recent introduction, there has been little time for a scientific body of evidence to develop on the health effects of e-cigarettes.

Public Health Consequences of E-Cigarettes reviews and critically assesses the state of the emerging evidence about e-cigarettes and health. This report makes recommendations for the improvement of this research and highlights gaps that are a priority for future research.

  1. ×

    Welcome to OpenBook!

    You're looking at OpenBook, NAP.edu's online reading room since 1999. Based on feedback from you, our users, we've made some improvements that make it easier than ever to read thousands of publications on our website.

    Do you want to take a quick tour of the OpenBook's features?

    No Thanks Take a Tour »
  2. ×

    Show this book's table of contents, where you can jump to any chapter by name.

    « Back Next »
  3. ×

    ...or use these buttons to go back to the previous chapter or skip to the next one.

    « Back Next »
  4. ×

    Jump up to the previous page or down to the next one. Also, you can type in a page number and press Enter to go directly to that page in the book.

    « Back Next »
  5. ×

    Switch between the Original Pages, where you can read the report as it appeared in print, and Text Pages for the web version, where you can highlight and search the text.

    « Back Next »
  6. ×

    To search the entire text of this book, type in your search term here and press Enter.

    « Back Next »
  7. ×

    Share a link to this book page on your preferred social network or via email.

    « Back Next »
  8. ×

    View our suggested citation for this chapter.

    « Back Next »
  9. ×

    Ready to take your reading offline? Click here to buy this book in print or download it as a free PDF, if available.

    « Back Next »
Stay Connected!