sterilization

Voluntary sterilization: the clinical possibilities

Sterilization refers to the procedure performed to stop fertility permanently, in either the male or the female. It is the most reliable type of contraception; consequently it is the most common form of contraception in couples over the age of 35 in the UK who have completed their families.

Fertilization occurs when a man's sperm reaches and joins an egg released from the ovary of a woman. The released egg is picked up by one of the two Fallopian tubes, which transports it to the uterus. Fertilization usually occurs in the Fallopian tube; if fertilized, the egg then implants into the wall of the uterus to establish a pregnancy. Sterilization interrupts this process permanently, either by preventing the release of sperm or by stopping fertilization by blocking the Fallopian tube.

Female sterilization

may be achieved by a number of techniques, over a hundred having been described since Lungren performed what is thought to be the first tubal sterilization in 1880. Operations on women are commonly called tubal ligation, as the procedures aim to occlude or ‘ligate’ (tie) the Fallopian tubes. The majority of operations described involved cutting the Fallopian tube and oversewing the cut end so that it was hidden. These operations required an incision either on the abdominal wall or through the top of the vagina to gain access to the tubes. The early operations are thought to have had a failure rate of around 1 in 200.

Sterilization can be performed at the time of Caesarean section, which allows easy access to the Fallopian tubes. This is seldom done now, as the failure rate is higher than with other techniques applied after the womb has returned to its non-pregnant state.

Modern surgical techniques have been developed and now include laparoscopic (telescopic) procedures to occlude the Fallopian tubes. These may use diathermy (burning) of the tubes to damage them and seal them. Alternatively, one of two common types of device are used to block the tubes. The first type involves placing small rubber bands over a pinched-up portion of each tube. The second type involves placing a crushing clip across them.

If a sterilization procedure fails there is an increased risk of the pregnancy implanting outside the womb. This is known as an ectopic pregnancy, which most commonly occurs in the Fallopian tube and can sometimes, if the pregnancy grows, result in the tube rupturing and causing internal bleeding.

Male sterilization

is achieved by the operation of vasectomy: cutting or ligating, on both sides, the vas deferens, which transports sperm from the testicles to the penis. The major advantage to a couple of a vasectomy is that it is a much simpler operation than female sterilization, due to the easy access to the vas within the scrotum. Vasectomy can easily be performed as an outpatient operation under local anaesthetic. After the operation the man must wait for around twelve weeks before the sperm count falls to sterile levels. Normally doctors ask for two sperm samples to check the operation has worked before alternative contraception can be abandoned.

Men and women requesting sterilization are usually seen at least twice by doctors prior to being sterilized, as the operation is designed to be permanent. Although reversal may be possible, sterilization should not be performed if either of the partners is unsure. It is also important that the doctor excludes any medical reason why the operation should not be performed. Women who have been taking the contraceptive pill because of painful periods are warned that these may recur if the Pill is stopped.

Current research is investigating reversible forms of contraception such as foam plugs for the Fallopian tubes or for the vas deferens.

Eugenical sterilization as a solution to social problems

Eugenicists in the US were particularly active in lobbying for the passage of state eugenical sterilization laws in the 1920s and 30s. Similar movements occurred in Canada, Britain, and Germany, but no laws were passed. Scandinavian countries — Denmark, Norway, Sweden, and Finland — passed laws in the 1930s. In the US, Harry H. Laughlin, of the Eugenics Record Office in Cold Spring Harbor, had drawn up a ‘Model Sterilization Law’ that served as a prototype for local use at home or abroad. Although the earliest such laws had been passed before World War I, the majority were established in the inter-war period. Eugenical sterilization laws were considered quite different from the punitive sterilization laws that existed in many states and countries in the nineteenth century. Although both types were compulsory, eugenical sterilization was aimed at prevention of future problems rather than serving as a punishment for past ones.

Eugenical sterilization was always couched in medical and scientific terms, and was justified as a means of saving the taxpayer money. In most countries it was aimed specifically at those individuals in mental or penal institutions who, from family pedigree analysis, were considered likely to give birth to socially defective offspring. In the US, sterilization could be ordered only after a patient had been examined by a eugenics committee, usually composed of a lawyer or family member representing the individual; a judge; and a doctor or other eugenic ‘expert’. Lobbyists often included members of the local state American Eugenics Society and a network of progressive enthusiasts who thought this was the way to cure social problems at their roots — it was the prime example of ‘social efficiency’.

Between 1907 (when the first law was passed, in Indiana) and 1941, over 38 000 eugenical sterilizations were performed in the US, with California in the lead. By the early 1960s the number had risen to over 60 000. The most famous sterilization case was that of Carrie Buck in Virginia, where a test case was set up to determine whether the law which had been passed was constitutional. Buck v. Bell was tried in 1925 in the Virginia Circuit Court. When the lower court ruled in favour of the law, an appeal was sent to the Supreme Court of the US, where Justice Oliver Wendell Holmes wrote the majority report. In upholding the lower court ruling Holmes made his oft-repeated assertion: ‘Three generations of imbeciles are enough.’ More to the legal point, Holmes claimed that ‘The principle that sustains compulsory vaccination is broad enough to cover cutting the Fallopian tubes.’

Laughlin's model law served also as a basis for a similar law in Germany, passed by the National Socialist government in 1933. For this effort, as well as for his enthusiastic support of Nazi eugenics programmes, Laughlin was awarded an honorary doctorate from Heidelberg University in 1936 — three years after the Nazis had come to power, and two years after their sweeping sterilization act had gone into effect.

While it would not be historically accurate to claim that state sterilization laws were repealed en masse after World War II and the disclosure of Nazi eugenic excesses, the general trend in 1945–55 was a decline in their application, increasing challenges to their constitutionality, and repeal of laws in some states — but it was not, for example, until 1977 that New Jersey outlawed the compulsory sterilization of the ‘developmentally disabled’. More telling, perhaps, than legislative changes, is the history of the actual application of sterilization laws in the post-war era — where they were not repealed, there was a dramatic decrease in the number of sterilizations reported. This decline was partly due to changing attitudes about the actual genetic effectiveness of sterilization — the acceptance that feeblemindedness might not have such a hereditary basis as had been supposed.

Influenced by their proximity to the Nazi experience, the Scandinavian countries repealed their laws after World War II. However, related issues of sterilization and control of reproduction in other guises continued, and gained considerable momentum after 1950, with respect to world population growth. Funded by the Rockefeller Foundation, pilot population control programmes were initiated in India, Puerto Rico, and other Third World countries; by 1960 these had been taken over and expanded by the US government funded bodies. Some post-war proponents of population control had been involved in eugenics in the 30s and 40s, and they used comparable arguments to those advanced earlier for eugenical sterilization — the differential birthrate of non-Western, non-European/American peoples. Now on a global scale, population control was, in the words of historian and critic Allan Chase ‘aimed at the gonads of the poor’.

Linda Cardozo,, Philip Toozs-Hobson,, and Garland E. Allen

Bibliography

Allen, G. E. 1986. The eugenics record office at Cold Spring Harbor: an essay in institutional history. Osiris 2 (2nd Series), 224–64.
Chase, A. 1977. The legacy of Malthus. Alfred A. Knopf, New York.
Reilly, P. 1992. The surgical solution: a history of involuntary sterilization in the United States. Johns Hopkins University Press, Baltimore.

Sterilization

Sterilization is the result of any procedure or condition by which a person becomes incapable of reproducing. Sterilization may be voluntary and undertaken as a permanent form of birth control, or it may be involuntary, the result of disease, treatment (including surgery, drug therapy, or radiation), trauma to the reproductive organs (such as castration), or public policy (as for population control). Surgical sterilization—vasectomy in males and tubal ligation (salpingectomy) in females—is the most common form of contraception used in married couples ages thirty and above. Because it is considered permanent, married women are more apt to undergo sterilization than those who are unmarried. Even though female sterilization involves more invasive surgery, has more complications, costs more, and has a higher rate of failure than male sterilization procedures (0.4% for females, compared with 0.15% for males), the rate of female sterilization is roughly 19 percent, whereas that of males is around 12 percent. In the United States, insurance companies are more likely to pay for a woman's tubal ligation than for her male partner's vasectomy.

Males are sterilized generally through a vasectomy. This is usually performed in a doctor's office under local anesthesia. The entire procedure takes fifteen to twenty minutes. A small incision is made in the scrotal sac, and a small section of the vas deferens is isolated and drawn through the incision. The ends of the vas are then either tied off or cauterized to prevent the ends from growing back and rejoining. The operation works by preventing the sperm from reaching the urethra and thus the ejaculated seminal fluid. Men who have undergone vasectomies are generally able to resume normal sexual relations within days of the procedure, though they must continue to use alternative birth control methods until the sperm count shows no sperm. Usually by six weeks after the procedure or fifteen ejaculations, men who have undergone the procedure are essentially sterile and incapable of impregnating a woman. Failures within the first two months following the vasectomy are usually due to a few residual sperm remaining in the genital tract. Later failures are generally the result of the vas deferens growing back together. For the latter reason, doctors frequently suggest a repeat sperm count after one year from the procedure. Other complications include a local and temporary inflammation, discomfort, and (very rarely) a serious infection of the epididymis.

Sperm continues to be produced by the testes but is released into the abdominal cavity and reabsorbed by the body. Vasectomy does not diminish libido (sex drive) or cause any change in erectile or ejaculatory function, nor does it noticeably diminish the volume of the ejaculate (since sperm normally only accounts for 1% of the seminal fluid). Male hormones, including testosterone, are still produced. Though vasectomy is considered a permanent form of sterilization, the procedure may be reversed in a vasovasotomy, in which the ends of the vas deferens are surgically reconnected. Success rates vary from 16 percent to 79 percent.

Tubal sterilization, also called tubal ligation (having one's tubes tied), is the most common method of female sterilization. During this procedure, the fallopian tubes are cut and cauterized (or otherwise occluded) to prevent the ova from reaching either the sperm or the uterus. There are several surgical means to accomplish this, including both abdominal and vaginal approaches. Laparoscopy is a minimally invasive method whereby a small incision is cut in the abdomen (or navel, in what is sometimes called belly-button surgery). The fallopian tubes are then isolated with a lighted laparoscope and looped out through the incision where they are either severed or tied. The tubes then slide back into the abdominal cavity. The procedure may be done on an outpatient basis, and women may return to their routines and resume sexual intercourse when discomfort subsides.

A laparotomy is more invasive and involves a larger incision. Women who elect to undergo tubal ligation immediately after a Cesarean section will undergo this type of surgery. A minilaparotomy (or minilap) employs similar technique but requires a smaller incision. Tubal ligation may also be performed vaginally, with the fallopian tubes severed through an incision on the back wall of the vagina (and thus leaving no visible scar). In addition, the Essure method, developed in 2002, uses hysteroscopy (a tube with a video and light source attached) to guide the placement of micro-inserts (elongated plugs) at the opening of each of the fallopian tubes in the uterus. Over the following three months, scarring develops and blocks sperm from entering the tubes to fertilize the egg. The advantage to the latter method is that it may be done in the doctor's office under local anesthesia. The downside is that, because there is a relatively high failure rate immediately following the insertion, the woman must undergo a hysterosalpingogram (a type of X-ray) three months after the procedure to confirm that the tubes are adequately occluded.

None of the previous methods disrupts the woman's sexual drive or response. Nor do they induce premature menopause, as hormone secretion is undisturbed. Women who have a tubal ligation will continue to ovulate and menstruate (though the unfertilized egg will be reabsorbed by the body). The procedure is considered permanent because it is difficult (and expensive) to reverse.

A hysterectomy may also result in sterilization, though it is not considered a method of voluntary sterilization. It is generally performed as a treatment for cancer or other disease of the reproductive tract. Hysterectomy with removal of the ovaries (oophorectomy) will put a woman into surgical menopause because of a profound reduction of the secretion of the hormones estrogen and progesterone.

When pregnancy does occur following a tubal ligation, there is a high incidence of ectopic pregnancy because of the tubal occlusion. Ectopic pregnancies are more likely to occur two or more years following the procedure rather than immediately following it. Vaginal procedures have higher failure rates and are more subject to infection than laparoscopic or minilaparotomy techniques.

Sterilization can also occur as the result of disease or treatment (such as chemotherapy or radiation). Untreated sexually transmitted disease may render the infected person (male or female) infertile resulting in irreversible sterility by causing scarring and occlusion in the reproductive organs.

Historically, because of high infant and child mortality rates, survival of societies depended on the fertility and fecundity of its inhabitants. A lack of understanding about reproduction led to many superstitions and folk stories about fertility. In ancient Mesopotamia the test for permanent infertility was to have a woman drink a concoction made of a hollowed-out watermelon and the breast milk of a woman who has produced a male child. If the woman in question vomited, she was thought to be able to bear a child; if she belched, she was deemed sterile and unable to conceive.

Instances of forced or involuntary sterilization involve issues of eugenics (trying to improve the gene pool of a society) and overpopulation. One of the more egregious programs for compulsory sterilization was practiced by Nazi Germany. In an effort to create an ideal Aryan race, the government oversaw the sterilization of over 400,000 people. These programs also existed in other countries. Sweden sterilized roughly 0.1 percent of its population (mostly criminals, mental patients, and as a condition for receiving social welfare benefits). The United States also targeted the mentally and physically impaired (including those with epilepsy, blindness, and deafness). Native Americans and African Americans were singled out in an effort to limit large families. In 2003 the North Carolina Legislature repealed the last of its eugenics laws, which were initially passed in an attempt to eliminate mental illness and genetic defects in the state. In a 2004 case, controversy arose over the decision by a couple to remove the reproductive organs of their mentally and physically handicapped daughter in an effort to keep her physically immature and smaller so that they could continue to care for her at home. Involuntary sterilization still occurs in the United States, but states very often require evidence of therapeutic benefit to the person before allowing the procedure.

In countries desperate to find a way to deal with exploding population growth, a major advantage of sterilization is its effectiveness (nearly 100%) and its permanence. Between 1976 and 1977, the Indian government under Indira Gandhi (1917–1984) began an aggressive program that both rewarded men and women for undergoing sterilization by offering them financial incentive (or in some cases a transistor radio) or coerced them with the threat of being arrested; it was proposed that parents with two children agree to be sterilized or else go to jail for two years. Rural areas were set in sterilization competitions with one another, with the winner receiving preferential status for irrigation facilities and fresh drinking water. People expressed fear of appearing in public places lest they be picked up by sterilization teams. Public outcry against coerced sterilization derailed the program. Human rights groups have censured countries such as Slovenia and Peru for supporting coerced sterilizations. China is particularly targeted for imposing forced sterilization (among other reproductive control policies) on its population to reach its one-child policy goals.

see also Castrati.

BIBLIOGRAPHY

Gunther, Daniel F., and Douglas S. Diekema. 2006. "Attenuating Growth in Children with Profound Developmental Disability: A New Approach to an Old Dilemma." Archive of Pediatric Medicine 160: 1013-1017.

Seeley, Rod R.; Trent D. Stephens; and Philip Tate. 1991. Essentials of Anatomy and Physiology. St. Louis, MO: Mosby.

Speroff, Leon; Robert H. Glass; and Nathan G. Kase. 1994. Clinical Gynecologic Endocrinology and Infertility. 5th edition. Baltimore: Williams and Wilkins.

Tannahill, Reay. 1980. Sex in History. New York: Stein and Day.

                                           Diane Sue Saylor

Sterilization

Introduction

History and Scientific Foundations

Applications and Research

Impacts and Issues

BIBLIOGRAPHY

Introduction

Sterilization refers to processes that eliminate microorganisms from surfaces, the interior of equipment, foods, and liquids. A catheter is one example of a device whose surface must be completely sterilized before it is inserted in a person to deliver food or medicine. A cardiac pacemaker is another example of a device whose surface must be sterilized before it is implanted inside the body to control the heart rate. A common example of a liquid requiring sterilization is the liquid-based nutrient medium used to grow bacteria in the laboratory.

Sterilization is intended to eliminate living microorganisms such as bacteria, fungi, and protozoa, along with nonliving microbes such as viruses that, given the appropriate host, can cause disease.

There are various methods of sterilization depending on the aim of the procedure. For example, surgical instruments are sterilized to guarantee the absence of pathogens (disease-causing organisms), while most laboratory growth media used for experimentation is sterilized to guarantee the absence of bacteria. Pharmaceutical medications also need to be free of all potential disease-causing agents.

WORDS TO KNOW

AUTOCLAVE: An autoclave is a device that is designed to kill microorganisms on solid items and in liquids by exposure to steam at a high pressure.

PATHOGEN: A disease causing agent, such as a bacteria, virus, fungus, etc.

History and Scientific Foundations

Heat has been used to sterilize objects for millennia. Until a few centuries ago, the flame of a fire was used. Today, the most common method of heat sterilization employs high temperature and pressure above atmospheric pressure. The combination of temperature and pressure most efficiently heats an object or a volume of liquid; exposure of the samples for a certain period of time has proved sufficient to kill even hardy microorganisms.

An autoclave is the most common instrument used for heat sterilization. Autoclaves range in size from small units that easily fit on the bench-top of a laboratory to large units that have the volume of an average kitchen refrigerator. An autoclave uses steam to sterilize the objects place inside it. Most typically, the steam is pumped into the autoclave chamber at a temperature of 250°F (121°C) and a pressure that is 15 pounds per square inch above atmospheric pressure. These conditions of temperature and pressure are maintained for at least 15 minutes (larger loads or greater volumes of liquid can be held longer). Then, the steam is released from the chamber in a controlled and safe manner. The chamber can be opened when it has returned to atmospheric pressure.

As a control over the process, indicator tape can be applied to the objects being autoclaved. Bands form on the tape when the proper conditions of temperature, pressure, and time have been attained. This helps the operator judge whether sterilization has been successful. To be even more certain, solutions that contain bacterial spores of Bacillus stearothermophilus can be included with the load being sterilized. Bacterial spores are very resistant to the killing action of heat. If the liquid containing the spores is incubated in a suitable liquid growth source and the medium remains clear, it indicates that sterilization was successful. In addition to the use of this so-called bio-indicator, many autoclaves record the temperature profile of each sterilization cycle, allowing the user to visually monitor whether the appropriate conditions were achieved.

Monitoring of autoclave performance is important. If, for example, too many items are autoclaved at once, the overcrowded conditions may not allow the steam to effectively penetrate the entire load, which can result in inadequate sterilization.

Although autoclaving is an effective method of sterilization with many applications, it is not foolproof. For example, it has been shown that prions—proteins whose abnormal folding stimulates damage of brain cells causing several similar diseases termed transmissible spongiform encephalopathies (an example is Creutzfeld-Jacob disease)—can remain potent following autoclaving of surgical instruments. Even the combination of autoclaving with chemicals has proven ineffective against prion contamination. The World Health Organization has recommended that surgery on patients suspected of having a prion-related disease be performed with disposable instruments, or that the instruments used be incinerated after the surgery is completed.

There are other methods of sterilization. Some metal objects can be surface-sterilized by holding them in an open flame. This is a common way of sterilizing a loop of metal called an inoculating loop that is used to transfer microorganisms from one place to another during experiments. Burning trash that contains medical waste is another way of sterilizing the residual ash. This ash can then be safety disposed of. Medical incinerators must be specially designed to retain the vapor given off, since infectious material can potentially be carried into the air during incineration. A common method for sterilizing drinking water is boiling. Boiling kills most bacteria and inactivates most viruses. However, agents like prions and some spore-forming bacteria can survive boiling for 15 minutes. However, in most situations, boiling is better than not treating water at all before drinking it.

Objects such as plastic, optical equipment, and electrical circuits that cannot stand heat can be sterilized using a chemical called ethylene oxide. This chemical is applied as a gas in a specialized machine. Another sporeforming bacterium, Bacillus subtilus, is used to monitor the success of ethylene oxide sterilization.

Ozone is another chemical sterilizer. Drinking water can be sterilized using ozone. A diluted solution of bleach (sodium hypochlorite) is an especially useful sterilizing agent for work surfaces. Other chemical sterilizers include glutaraldehyde and hydrogen peroxide.

Applications and Research

Sterilization is a necessity of everyday life in research, health care, and even the supermarket. Ongoing investigations seek to develop chemicals that sterilize more efficiently and quickly, while being safe to use.

IN CONTEXT: BACTERIA SPORES SPUR STERILIZATION RESEARCH

The discovery of bacteria that are resistant to sterilization could potentially contaminate experiments and environments studied by NASA and other space agency probes. One species was tentatively named B. odysseensis after being isolated from the surfaces of the Mars Odyssey spacecraft following routine sterilization. The method of spore formation is suspected of having a role in resistance of spore-forming bacteria to sterilization.

Earth-bound benefits of such research offer hope of improved methods of sterilization and prevention of unintentional contamination.

SOURCE: Jet Propulsion Laboratory, National Aeronautics and Space Administrations (NASA)

Impacts and Issues

Without the ability to sterilize growth media, many scientific experiments could not be accomplished, as it would be impossible to know if the results were due to the organism being studied or to a contaminant. In addition, surgeries would have a very poor survival rate, as was the case in the days before sterilization techniques were routinely employed.

In some instances, standard sterilization methods have not been sufficient to protect patients from developing disease as a result of contact with contaminated medical equipment. An example occurred in 2003 in the Canadian province of New Brunswick, where seven patients probably contracted Creutzfeld-Jacob disease from prion-contaminated instruments used during their neurosurgeries. The instruments became contaminated when used in an operation on a patient who was subsequently found to have the disease. The instruments were routinely sterilized, but it later became clear that this routine sterilization procedure did not remove the prions. It was this outbreak that resulted in the institution of hospital protocols mandating the use of disposable instruments during procedures on high-risk areas such as the brain and spinal cord involving patients suspected of having a prion-related disease.

Recently, scientists have found that prions can be digested by a particular enzyme. Enzymatic treatment of medical instruments has shown promise as sterilization technique effective for prions, but it is not yet in general use.

While important, the quest for sterilization can go too far. One example is the marketing of surface sterilizing products designed for use in the kitchen and bathroom. Bacteria that are not killed by these products have the potential to become resistant to the particular chemical, which can make these bacteria a more serious concern than before they developed this resistance.

See AlsoDisinfection; Infection Control and Asepsis; Sanitation.

BIBLIOGRAPHY

Books

Gladwin, Mark, and Bill Trattler. Clinical Microbiology Made Ridiculously Simple. 3rd ed. Miami: Medmaster, 2003.

Prescott, Lansing M., John P. Harley, and Donald A. Klein. Microbiology. New York: McGraw-Hill, 2004.

Tortora, Gerard J., Berell R. Funke, and Christine L. Case. Microbiology: An Introduction. New York: Benjamin Cummings, 2006.

Brian Hoyle

Sterilization

Sterilization is a term that refers to the complete killing or elimination of living organisms in the sample being treated. Sterilization is absolute. After the treatment the sample is either devoid of life, or the possibility of life (as from the subsequent germination and growth of bacterial spores), or it is not.

There are four widely used means of sterilization. Standard sterilization processes utilize heat, radiation, chemicals, or the direct removal of the microorganisms .

The most widely practiced method of sterilization is the use of heat. There are a number of different means by which heat can be applied to a sample. The choice of which method of delivery depends on a number of factors including the type of sample. As an example, when bacterial spores are present the heating conditions must be sufficient to kill even these dormant forms of the bacteria .

A common type of heat sterilization that is used many types each day in a microbiology laboratory is known as incineration. Microorganisms are burned by exposing them to an open flame of propane. "Flaming" of inoculating needles and the tops of laboratory glassware before and after sampling are examples of incineration.

Another form of heat sterilization is boiling. Drinking water can be sterilized with respect to potentially harmful microorganisms such as Escherichia coli by heating the water to a temperature of 212°F (100°C) for five minutes. However, the dormant cyst form of the protozoan Giardia lamblia that can be present in drinking water, can survive this period of boiling. To ensure complete sterility, the 212°F (100°C) temperature must be maintained for 30 minutes. Even then, some bacterial spores, such as those of Bacillus or Clostridium can survive. To guarantee sterilization, fluids must be boiled for an extended time or intermittent boiling can be done, wherein at least three—and up to 30—periods of boiling are interspersed with time to allow the fluid to cool.

Steam heat (moist heat) sterilization is performed on a daily basis in the microbiology laboratory. The pressure cooker called an autoclave is the typical means of steam heat sterilization. Autoclaving for 15 minutes at 15 pounds of pressure produces a temperature of 250°F (121°C), sufficient to kill bacterial spores. Indeed, part of a quality control regiment for a laboratory should include a regular inclusion of commercially available bacterial spores with the load being sterilized. The spores can then be added to a liquid growth medium and growth should not occur.

Pasteurization is employed to sterilize fluids such as milk without compromising the nutritional or flavor qualities of the fluid.

The final form of heat sterilization is known as dry heat sterilization. Essentially this involves the use of an oven to heat dry objects and materials to a temperature of 320–338°F (160–170°C) for two hours. Glassware is often sterilized in this way.

Some samples cannot be sterilized by the use of heat. Devices that contain rubber gaskets and plastic surfaces are often troublesome. Heat sterilization can deform these materials or make them brittle. Fortunately, other means of sterilization exist.

Chemicals or gas can sterilize objects. Ethylene oxide gas is toxic to many microorganisms. Its use requires a special gas chamber, because the vapors are also noxious to humans. Chemicals that can be used to kill microorganisms include formaldehyde and glutaraldehyde. Ethanol is an effective sterilant of laboratory work surfaces. However, the exposure of the surface to ethanol must be long enough to kill the adherent microorganisms, otherwise survivors may develop resistance to the sterilant.

Another means of sterilization utilizes radiation. Irradiation of foods is becoming a more acceptable means of sterilizing the surface of foods (e.g., poultry). Ultraviolet radiation acts by breaking up the genetic material of microorganisms. The damage is usually too severe to be repaired. The sole known exception is the radiation-resistant bacteria of the genus Deinococcus.

The final method of sterilization involves the physical removal of microorganisms from a fluid. This is done by the use of filters that have extremely small holes in them. Fluid is pumped through the filter, and all but water molecules are excluded from passage. Filters—now in routine use in the treatment of drinking water—can be designed to filter out very small microorganisms, including many viruses .

See also Bacterial growth and division; Bacteriocidal, bacteriostatic; Laboratory techniques in microbiology

STERILIZATION

Late in the nineteenth century, when simple and safe medical procedures for sterilization became available, the eugenics movement began to promote compulsory sterilization laws. A few laws were enacted specifying sterilization as punishment for sex crimes, but they were rarely enforced. In 1907 Indiana adopted a law authorizing sterilization of persons deemed "feebleminded," or, as one leading proponent put it, "socially defective." Other states soon followed. The Supreme Court lent both practical and moral support in its 1927 decision in buck v. bell, upholding the constitutionality of Virginia's law. By 1935 more than thirty states had adopted forced sterilization laws, and 20,000 "eugenic" sterilizations had been performed. The victims of such laws tended to be poor; indeed, in the view of eugenics proponents, poverty and other forms of dependence were the marks of the "socially inadequate classes" that needed eradication.

Times have changed, and constitutional law has changed. Concurring in griswold v. connecticut (1965), Justice arthur goldberg said, "Surely the Government, absent a showing of a compelling subordinating state interest, could not decree that all husbands and wives must be sterilized after two children have been born to them." After skinner v. oklahoma (1942) the point seems incontestable. Yet some state courts, following Buck, still uphold laws authorizing the involuntary sterilization of institutionalized mental patients. Although only fifteen years separated the Buck and Skinner decisions, their doctrinal foundations were worlds apart. Skinner, calling procreation "one of the basic civil rights of man," insisted on strict scrutiny by the Court of the justifications supporting a compulsory sterilization law. Buck, on the other hand, had employed a deferential form of rational basis review, analogizing forced sterilization to forced vaccination.

Skinner's crucial recognition was that sterilization was more than an invasion of the body; it was an irrevocable deprivation of the right to define one's life and one's identity as a biological parent. Vaccination implies no such consequences for one's self-identification and social role. The constitutional issues presented by sterilization thus bear a strong analogy to the issues raised by laws restricting other forms of birth control and abortion. (See freedom of intimate association.) The Supreme Court has characterized all these forms of state interference with reproductive autonomy as invasions of fundamental interests, and has subjected them to close scrutiny in the name of both equal protection, asin Skinner, and that form of substantive due process that goes by the alias of a right of privacy, asin Griswold and roe v. wade (1973).

The issue of Buck seems certain to return to the Supreme Court one day, to be decided on the basis of a much heightened standard of review. Similarly, a state law requiring consent of a spouse before a person could be sterilized would surely be held invalid, on analogy to planned parenthood of missouri v. danforth (1976). If a law calling for involuntary sterilization must pass the test of strict scrutiny, and if a competent adult has a corresponding right to choose to be sterilized, then the critical ingredient is choice. An "informed consent" requirement thus seems defensible against constitutional attack, provided that the required "informing" procedure does not unreasonably burden the decision to be sterilized. (An informed consent requirement for abortion was upheld by the Supreme Court in Danforth.)

As Justice william o. douglas noted in his Skinner opinion, sterilization in "evil or reckless hands" can be an instrument of genocide. Even the most devoted partisan of reproductive choice cannot be entirely comfortable knowing that the percentage of sterilized nonwhite women in the United States is almost triple that for white women, or that among public assistance recipients blacks are twice as likely to "choose" sterilization as are whites. Under current interpretations the Constitution has nothing to say about the bare fact of this disparity; yet it reflects a condition of constitutional dimension that deserves to be addressed, at least in the domain of procedural due process. And if nonwhite women are led by government officers to believe that sterilization is voluntary in theory but somehow compulsory in fact, that form of "engineering of consent" appears reachable in actions for damages under section 1983, title 42, united states code, based on the deprivation of substantive due process.

Kenneth L. Karst
(1986)

Bibliography

Kelly, Mary E. 1979 Sterilization Abuse: A Proposed Regulatory Scheme. DePaul Law Review 28:731–768.

Kevles, Daniel J. J. 1985 In the Name of Eugenics: Genetics and the Uses of Human Heredity. New York: Knopf.

Pilpel, Harriet F. 1969 Voluntary Sterilization: A Human Right. Columbia Human Rights Law Review 7:105–119.