RADIOACTIVE STRONTIUM-90 IN BABY TEETH

OF NEW JERSEY CHILDREN

AND THE LINK WITH CANCER: A SPECIAL REPORT

 

By

 

Joseph J. Mangano, National Coordinator

The Radiation and Public Health Project

 

Trenton NJ

MaY 19, 2003

 

 

 

 

 

 

 

RPHP Directors

 

Jay M. Gould, Ph.D.

Jane Gould, MA

Joseph Mangano, MPH, MBA

William McDonnell, MA

Ernest J. Sternglass, Ph.D.

 

TABLE OF CONTENTS

 

Item Page

 

Executive Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

 

 

Background - Health Effects of Radioactive Emissions . . . . . . . . . . . . . . . . 5

 

 

Evolution of New Jersey Study/Supporting Data . . . . . . . . . . . . . . . . . . . . . 8

 

 

Study Methodology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

 

 

Study Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

 

 

Discussion/Implications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

 

 

Appendices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

 

 

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27

 

Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30

 

 

 

 

EXECUTIVE SUMMARY

 

Since 1996, the Radiation and Public Health Project (RPHP) has conducted a study of radiation levels in the bodies of persons living near nuclear reactors. Specifically, it has measured Strontium-90 (Sr-90) concentrations in baby teeth. Strontium is chemically similar to calcium; after it enters the body by breathing, food, or water, it attaches to bone and teeth. Sr-90 has a slow decay rate, and remains in the body for many years.

 

One of the study's targets is the area near the Oyster Creek reactor in Ocean County. Health and safety concerns about Oyster Creek are reflected in the following data:

 

Major Meltdowns

 

 

 

Radioactivity Routinely Produced

 

 

High Childhood Cancer Rates Near Oyster Creek

 

 

 

 

The combination of several personal appearances in Toms River by actor Alec Baldwin, plus numerous appeals to the public by local activists appealing for tooth contributions resulted in 271 baby teeth submitted to RPHP by New Jersey residents. These teeth were all tested for Sr-90, and principal results of the analysis are as follows:

 

  1. The average concentrations of Sr-90 in baby teeth in Ocean and Monmouth counties, and northeast New Jersey are 21% above that of other New Jersey counties.

    2.  

  2. From 1986-89 to 1994-97, average Sr-90 levels in Ocean and Monmouth county steadily rose 50%, reversing a decline that began in the early 1960s. This pattern is similar to that in five other states where the majority of teeth have been collected.

    3.  

  3. In Ocean and Monmouth Counties, trends in Sr-90 are similar to trends in cancer deaths among children under age ten

 

The above results suggest that current reactor emissions - not old fallout from Nevada bomb tests in the 1950s and 1960s - account for a substantial proportion of radioactivity in the bodies of local children. More importantly, there is a statistical link between Sr-90 and childhood cancer in Ocean and Monmouth Counties.

 

Further studies, such as comparing Sr-90 in teeth of healthy children with teeth of children with cancer, are warranted. (RPHP has recently begun such a study). Moreover, any policy discussions concerning Oyster Creek should take into account the actual excess diseases and deaths caused by routinely-emitted low-dose radioactivity, along with a (hypothetical) catastrophic accident.

 

BACKGROUND - HEALTH EFFECTS OF RADIOACTIVE EMISSIONS

 

  1. General History of Reactors.

    2. After the discovery of fission that led to the Hiroshima and Nagasaki bombs in August 1945, scientists and government officials looked for alternative uses of man-made radioactive chemicals. President Eisenhower made his "Atoms for Peace" speech to the United Nations on December 8, 1953, suggesting that (among other uses), atomic power could generate electricity. (1) Congress passed the Atomic Energy Act in 1954, which allowed private companies to build nuclear power plants and ordered the federal Atomic Energy Commission to provide technical assistance. (2)

     

    The Shippingport reactor near Pittsburgh became the first nuclear power reactor to begin operations, in December 1957. Currently, 103 reactors are now licensed by the federal government to produce electricity (including Oyster Creek, and three reactors in Salem County). Since the late 1980s, nuclear power has generated about 20% of the electricity consumed in the U.S. (3)

     

  2. Health Effects of Radioactivity.

    3. Much consideration has been given to health effects of a large-scale meltdown of a reactor's core (where electricity is produced) and/or its spent fuel pools (where radioactive waste is stored). The discussion has been particularly serious since the terrorist attacks of September 11, 2001. Such a major meltdown at a reactor near a large city would constitute the worst environmental catastrophe in U.S. history, comparable to the 1986 Chernobyl accident.

     

    However, nuclear reactors pose health concerns other than major meltdowns. To produce electricity, each reactor must emit relatively low-dose amounts of airborne and liquid radioactivity into the environment. This radioactivity represents over 100 different isotopes only produced in reactors and atomic bombs, including Strontium-89, Strontium-90, Cesium-137, and Iodine-131. Humans ingest them either by inhalation, or through the food chain (after precipitation returns these airborne chemicals to earth).

     

    Each of these 100-plus chemicals has a special biochemical action; iodine seeks out the thyroid gland, strontium clumps to the bone and teeth (like calcium), and cesium is distributed throughout the soft tissues. All are carcinogenic. Each decays at varying rates; for example, Iodine-131 has a half-life of eight days, and remains in the body only a few weeks. Strontium-90 (Sr-90) has a half-life of 28.7 years, and thus remains in bone and teeth for many years.

     

    These chemicals are different from "background" radiation found in nature in cosmic rays and in the earth's surface. Background radiation, while still harmful, contains no chemicals that specifically attack the thyroid gland, bones, or other organs.

     

    Because no nuclear reactor in the U.S. has been ordered since 1978, the current crop of 103 reactors is aging, which presents additional health concerns. As reactors age, their parts are more likely to wear down and malfunction, raising the possibility of higher emissions and increased levels of environmental radioactivity. For example, in March 2002 officials noticed that corrosion from boric acid in the Davis-Besse reactor in Ohio had worn down a steel lid from six inches to three-eighths of an inch; that reactor has been closed for over a year to make needed repairs.

     

  3. Lack of Studies Comparing Low-Level Radioactivity with Disease Rates.

    4. Currently, federal regulators require annual reports from plant operators to submit annual reports of emissions and environmental (air, water, milk, soil) levels of radioactivity. If these levels fall below federally-defined "permissible limits" they are judged to be harmless, and the plant operator retains its license. The Nuclear Regulatory Commission, utilities that operate plants, and state health departments perform no studies evaluating any health risks of plant emissions or environmental radiation levels.

     

    For decades, scientists have documented harm from relatively low-dose exposures of radioactivity otherwise presumed to be safe. In the 1950s, British physician Alice Stewart found that pelvic X-rays to pregnant women nearly doubled the risk that the child would die from cancer by age 10. (4) In 1997, the National Cancer Institute estimated that up to 212,000 Americans developed thyroid cancer after ingesting fallout from above-ground nuclear weapons tests in Nevada. (5) In 2000, the U.S. Department of Energy acknowledged that thousands of workers in atomic weapons plants developed cancer and other diseases in excess of the expected. (6)

     

    Disease rates in persons living near nuclear power reactors have been reported in dozens of medical journal articles. For example, at least 12 studies have demonstrated high rates of childhood cancer near separate nuclear plants in the United Kingdom. (7-18) In the U.S., very few studies have been done on childhood cancer near nuclear plants; and these examined patterns from decades ago, were small in scale, and yielded mixed results. (19-22) Moreover, no study has ever been done comparing in-body radioactivity of persons living near U.S. nuclear plants with cancer risk. Thus, much remains to be learned on the health effects of nuclear reactor emissions.

     

  4. RPHP Baby Tooth Study - A Pioneering Effort.

In 1996, the Radiation and Public Health Project (RPHP) initiated the first-ever study of in-body radioactivity near U.S. nuclear plants. Known as the "Tooth Fairy Project," the study involved collecting discarded baby teeth and performing laboratory testing for levels of radioactive Sr-90. RPHP is a New York-based non-profit group of scientists and health professionals dedicated to researching the link between low-dose radiation exposures and disease. Since 1994, group members have written five books and published 18 articles in professional medical/scientific journals on this topic.

 

The Tooth Fairy Project is not unprecedented. A 1958-70 effort in St. Louis collected over 300,000 baby teeth and measured many of them for Sr-90 levels. The St. Louis project showed that because of fallout from atomic bomb testing in Nevada, children born in 1964 had about 50 times greater concentrations of Sr-90 than did children born in 1950. It also found that in-body levels of Sr-90 decreased by about 50% from 1964 to 1969, after the Partial Test Ban Treaty signed by President Kennedy and Premier Khrushchev relegated all testing to underground sites. (23)

 

In recent years, there have been at least four studies of Sr-90 from nuclear reactor emissions in baby teeth outside of the U.S. Three of these addressed fallout from the Chernobyl accident in Germany, Greece, and the Ukraine (24-26), while the other examined releases from the Sellafield plant in western England (27). However, none of these compared releases to disease patterns.

 

To bridge the knowledge gap due to lack of prior research, the RPHP baby tooth study set the following goals:

 

  1. To measure patterns of Sr-90 concentrations in baby teeth near U.S. nuclear reactors.

    2.  

  2. To compare Sr-90 patterns with those of cancer and other diseases.

 

To date, RPHP has collected over 4000 baby teeth, of which laboratory results of Sr-90 levels are available for over 3400. Most of these teeth are from children born since the mid-1980s living close to one or more nuclear reactors.

 

RPHP researchers have already published three medical journal articles on preliminary results. (28-30) The three principal findings are

 

  1. Current Sr-90 levels in children are similar to St. Louis children born in the late 1950s, during the time of above-ground bomb testing.

    2.  

  2. Levels have risen during the 1990s, suggesting that a current source of radioactive emissions is contributing to the burden on the body. Because Sr-90 is only produced in atomic bombs and nuclear reactors, the logical conclusion is that current rises likely represent reactor emissions.

    3.  

  3. In Suffolk County, NY, where over 500 teeth have been tested, the recent trend in Sr-90 is nearly identical to the trend in childhood cancer, suggesting a cause-and-effect relationship.

 

EVOLUTION OF NEW JERSEY STUDY/SUPPORTING DATA

 

Early in the baby tooth study, concerned local citizens near Oyster Creek contacted RPHP expressing interest in participating. Actor Alec Baldwin made visits to Toms River on November 9, 1999, February 29, 2000, and May 3, 2000 to raise awareness of the risks posed by Oyster Creek, and to appeal for contributions of baby teeth. In addition, members of Jersey Shore Nuclear Watch, a local advocacy group, made numerous local appearances appealing for teeth. One local resident, Barbara Bailine, dressed herself in a Tooth Fairy costume at various public events, which increased recognition of the study.

 

Due to these efforts, 538 teeth from New Jersey had been sent to RPHP as of April 2003. ("New Jersey teeth" represents tooth donors whose mother lived in the state during pregnancy, since the Sr-90 level at birth is calculated). Only New York and Florida contributed more teeth to the study. The total number of teeth received by April 5, 2003 was 4036.

 

Preliminary results of the study were presented at a press conference in Toms River on April 26, 2001. A total of 206 teeth were analyzed, including 182 from persons born in the 1980s and 1990s. These children should have little Sr-90 in their body from pre-1963 above-ground atomic bomb tests; most in-body radiation represents current sources.

 

New Jersey media reported various findings (similar to the national findings listed on page 7). The public attention from the announcement spurred the contribution of many more baby teeth.

 

A. Types of Reactor Emissions Posing Health Threats

Oyster Creek is the oldest of the 103 currently-operating nuclear reactors. It "went critical" (began producing electricity) on May 3, 1969, over 34 years ago. Thus far, the longest-running U.S. reactor was Big Rock Point in northern Michigan, which ran from 1962-87, just under 35 years.

 

There are four types of public health risk posed by reactors like Oyster Creek.

  1. Meltdown After Terrorist Attack.

Health concerns about Oyster Creek and all nuclear reactors rose after September 11, 2001. There has been a prolonged debate about the vulnerability of reactors to a terrorist strike, and the horrifying health consequences. In 1982, the Nuclear Regulatory Commission estimated the casualties after a reactor core meltdown. The Oyster Creek estimates were 13,000 rapid deaths from and 10,000 rapid cases of radiation poisoning, along with 23,000 eventual cancer deaths. These figures should be seen as conservative because they only consider

 

 

Because Oyster Creek lies just 60 miles south of New York City and 60 miles east of Philadelphia, the most densely populated area in the U.S., particular concern should be raised about the threat of a terrorist attack against this reactor.

 

2. Meltdown After Mechanical Failure.

A terrorist attack is not the only way in which a reactor meltdown can occur; mechanical failure is the other. The Chernobyl plant suffered a full meltdown of its core in 1986, while Three Mile Island Unit 2 in Pennsylvania experienced a partial meltdown in 1979, closing the reactor permanently.

 

Because the Oyster Creek (and other) reactors are aging, there is greater concern about parts being more likely to wear out, leak, or corrode. This concern was illustrated in March 2002 at the Davis-Besse plant (see page 6).

 

Adding to the concerns of the mechanical failure is the recent tendency of plant operators to run aging reactors more of the time. From 1970-94, Oyster Creek operated 67.0% of the time (U.S. average 75%), often closing for routine inspections and to repair mechanical failures. From 1995-99, this "capacity factor" rose sharply to 88.6%, as the national average was between 80 and 85 percent. (31)

 

3. Waste Buildup.

Each nuclear plant accumulates highly radioactive waste, known as "spent fuel rods." These resemble 10-foot long steel rods about the diameter of a pencil, containing high levels of radioactivity, and must be placed in 40 feet deep pools of constantly-cooled water. Oyster Creek, running out of pool space, began transferring some of the older rods to "dry cask" storage, or thick concrete containers. The U.S. government is planning to eventually store all waste at Yucca Mountain Nevada, but this plan is being contested in the courts, and the earliest possible date that waste transfers would begin is 2010. Whether the waste remains on site, or is transferred to Nevada, there is a chance that a terrorist attack or mechanical failure could cause a large-scale meltdown.

 

4. Routine Emissions.

While most radioactivity produced in reactors is contained in the building and stored as waste, a small proportion of this mix of 100-plus carcinogenic chemicals escapes through the stacks of the reactor. These tiny particles and gases present a concern for public health, since it enters the human body by breathing or through the food chain, after precipitation brings it to reservoirs, dairies, and other sources of food and water.

 

The Nuclear Regulatory Commission issued comparative records for all reactors until it ceased this publication in 1993. Prior to that time, Oyster Creek had the highest lifetime emissions of any single operating U.S. reactor. Emissions totaled 77 trillion picocuries (a measure of radioactivity) released into the air; this includes only chemicals with a half-life of more than eight days, or those most likely to enter the human body. This figure is more than five times greater than the official tally of 14 trillion emitted into the air at Three Mile Island during the 1979 accident.

 

RPHP's work is largely confined to health effects from routine emissions. To date, there have been no Chernobyl-type major accidents at U.S. reactors, and the hazardous waste is not actively involved in the food chain. Thus, the only ACTUAL exposure to radiation that reactors have posed to the public is from routine emissions.

 

B. Health Data Suggesting Harm to Residents Near Oyster Creek

Various pieces of evidence suggest that Oyster Creek emissions may increase the local risk of cancer.

 

1. Tom's River Cancer Cluster.

In 1997, the New Jersey Department of Health and the U.S. Centers for Disease Control and Prevention declared an official cancer cluster among children in Dover Township (Toms River), located just nine miles north (downwind) of the Oyster Creek plant. (32) From 1979 to 1995, 90 local cancer cases among children age 0-19 were confirmed, compared to an expected number of 67.

 

As public health officials attempted to determine factors behind the cluster, radioactive emissions from nuclear reactors was proposed as one, by experts like Dr. Helen Caldicott. (33) After an investigation lasting six years and costing $10 million dollars, state health officials released their final report on Toms River in December 2001. It found that environmental causes could only explain a small part, at best, of the epidemic. Furthermore, the state report found that emissions from Oyster Creek would only cause one case of cancer diagnosed over a lifetime for every ONE BILLION persons living nearby. RPHP regards this as a spurious conclusion based on faulty methods. A much more thorough analysis, using more appropriate techniques, must be employed before any conclusion is reached.

 

2. Childhood Cancer in Ocean and Monmouth Counties.

Statistical information reveals that high levels of childhood cancer in the Oyster Creek area extend beyond Dover Township, to include all of Ocean and Monmouth Counties. Table 1 shows that in 1981-2000, cancer incidence in children age 0-9 in the two counties exceeded the U.S. rate by about 24%. The higher local rate is statistically significance (p<.001). The most recent data (1996-2000) shows this high rate is continuing. A total of 523 children in the two counties have been diagnosed with cancer before their 10th birthday in the past 20 years.

 

The 1995-99 cancer mortality rate age 0-9 in Ocean and Monmouth, which lie downwind from Oyster Creek was +43.6% higher than the nation, and +26.0% higher than the state. The two-county cancer mortality actually increased by +20.2% from the early 1980s to the late 1990s, rising from 21 to 34 deaths. This pattern is quite unusual, because improvements in treatment have meant reductions in cancer deaths for children throughout the nation. The mortality rate declined -22.9% and -35.4%, respectively, for other counties in New Jersey and for the U.S. The difference with the nation is significant (p<.02) and of borderline significance with the state (p<.08).

 

Table 1

TRENDS IN CANCER INCIDENCE AND MORTALITY

OCEAN AND MONMOUTH COUNTY CHILDREN

 

Incidence (Cases Newly Diagnosed)

Area Cases, Age 0-9 Avg. Pop. 0-9 Cases/100,000

2 Cos. 1981-2000 523 2,720,723 19.22

U.S. 1981-2000 15.50 (est.)

 

2 Cos. 1996-2000 149 774,291 19.24

U.S. 1996-2000 15.85

 

Excess Ocean, Monmouth Over U.S., 1996-2000 +21.3% p<.10

1981-2000 +24.0% p<.001

 

Sources: New Jersey Cancer Registry, Trenton NJ (New Jersey data). Cancer registries for Atlanta, Connecticut, Detroit, Hawaii, Iowa, New Mexico, San Francisco, Seattle, and Utah (U.S. data).

 

 

Mortality (Deaths), 1995-99

Area Deaths, Age 0-9 Avg. Pop. 0-9 Deaths/100,000

Ocean, Monmouth 34 153,988 4.42

Other New Jersey 173 987,255 3.51

U.S. 5984 38,925,023 3.07

Excess Ocean, Monmouth Over U.S. +43.6%

Excess Ocean, Monmouth Over Other N.J. +26.0%

 

 

Mortality (Deaths), Ocean and Monmouth Counties, since 1979

5-Year Period Deaths, Age 0-9 Avg. Pop. 0-9 Deaths/100,000

1980-84 21 114,346 3.67

1985-89 26 126,415 4.11

1990-94 29 141,374 4.10

1995-99 34 153,988 4.42

Change 1980-84 to 1995-99

- Ocean, Monmouth +20.2% p<.01

- U.S. -35.4%

- Other New Jersey -22.9%

 

Ocean, Monmouth change statistically different than U.S. change (p<.02) and other NJ change (p<.08)

 

Notes: All portions of Ocean and Monmouth are located less than 40 miles of the Oyster Creek reactor, and downwind. Prevailing winds are from the south in Atlantic City.

 

Sources: National Center for Health Statistics (available from http://www.cdc.gov, data and statistics, CDC Wonder). Uses ICD-9 codes 140.0-239.9 (neoplasms). Bair FE. Weather of U.S. Cities, 4th Edition. Detroit: Gale Research Company Inc., 1992 (prevailing wind directions).

 

3. Adolescent/Young Adult Cancer in Ocean and Monmouth Counties.

Patterns of elevated local cancer rates are not just restricted to children, but to adolescents and young adults as well. In Ocean and Monmouth Counties, the 1995-99 death rate from cancer for persons age 10-24 was 16.2% above the U.S. and 17.5% above the remainder of New Jersey (Table 2). A total of 45 persons in this age category died from cancer in the latest five-year period. These levels are not as elevated as children under age ten, but still consistent with the pattern for the youngest residents.

 

Table 2

TRENDS IN CANCER INCIDENCE AND MORTALITY

OCEAN AND MONMOUTH COUNTY, AGE 10-24

 

Mortality (Deaths), 1995-99

Area Deaths, Age 10-24 Avg. Pop. 10-24 Deaths/100,000

Ocean, Monmouth 45 191,418 4.70

Other New Jersey 266 1,328,926 4.00

U.S. 10574 52,287,033 4.05

Excess Ocean, Monmouth Over U.S. +16.2%

Excess Ocean, Monmouth Over Other N.J. +17.5%

 

Notes: All portions of Ocean and Monmouth are located less than 40 miles of the Oyster Creek reactor, and downwind. Prevailing winds are from the south in Atlantic City.

 

Sources: National Center for Health Statistics (available from http://www.cdc.gov, data and statistics, CDC Wonder). Uses ICD-9 codes 140.0-239.9 (neoplasms). Bair FE. Weather of U.S. Cities, 4th Edition. Detroit: Gale Research Company Inc., 1992 (prevailing wind directions).

 

  1. Demographic Data Suggests Area Shouldn't Be at High Risk for Cancer.

The population of Ocean and Monmouth Counties, approaching 1.2 million, does not appear to have any of the demographic characteristics that are often associated with elevated health risks (Table 3). For example, there is a much higher percentage of non-Hispanic whites - who often carry a lower health risk than minorities - than in the rest of the state. Fewer live in poverty, which can often pose obstacles to good preventive or therapeutic medical care. However, Ocean County has a lower percentage of college graduates (Monmouth's is higher); more educated persons often better know how to practice effective preventive health and navigate the health system when seeking care.

 

Table 3

SELECTED DEMOGRAHPIC CHARACTERISTICS

OCEAN AND MONMOUTH COUNTIES VS. NEW JERSEY

 

Item Ocean Monmouth New Jersey

Population, 2000 510,916 615,301 8,414,350

 

% White, Non-Hispanic, 2000 89.9% 80.6% 66.0%

 

% Adults >24 with Bachelor's, 1999 19.5% 34.6% 29.8%

 

% Persons Below Poverty, 1999 7.0 6.3 8.5

 

Source: U.S. Census Bureau, 2000 Census of the Population. Obtained on February 3, 2003 on www.census.gov, quickfacts.

METHODOLOGY

 

A. Collecting Teeth.

As described above, most of the teeth collected in New Jersey were either due to personal appearances by Alec Baldwin or public appeals from the Jersey Shore Nuclear Watch group. These in turn generated media coverage, and parents learning about the project submitted their children's teeth to RPHP. Although these teeth are not necessarily representative of New Jersey's population - i.e., most are from the area nearest the Oyster Creek reactor - the large number of teeth makes it more likely the study results will be significant.

 

  1. Testing Teeth.

    2. RPHP measures the amount of Strontium-90 in each baby tooth by contracting with REMS, Inc., a laboratory in Waterloo, Ontario, Canada under the direction of Hari Sharma, PhD, a radiochemist. RPHP sends teeth to the laboratory in batches, and teeth are tested individually using a scintillation counter. All lab personnel are "blinded" about all information concerning each tooth, that is, they know nothing about what state it is from, how old the child is, etc. This "blinding" helps assure objective, non-biased results.

     

    The laboratory measures the concentration of Sr-90; specifically, it calculates the picocuries of Sr-90 per gram of calcium in each tooth. (See Appendix 1 for more specific technical procedures). The strontium-to-calcium ratio has been used in the St. Louis study in the 1960s, and all other recent baby tooth studies mentioned earlier. Effects of harmful strontium can be negated by health-promoting calcium.

     

    The laboratory returns results to RPHP, where staff converts the ratio to that at birth, using the Sr-90 half-life of 28.7 years. For example, if the lab determines the tooth had 3.00 picocuries of Sr-90 per gram of calcium, and the person was 28.7 years old, the ratio at birth would be 6.00 (half of the Sr-90 would have decayed in 28.7 years). RPHP computerizes the results, and produces summary reports.

     

    The Sr-90/Ca ratio for a single tooth is not a precise number because a typical baby tooth is small in mass and subject to some error. In fact, only the most modern machines can test individual teeth with any precision; the St. Louis study only tested batches of teeth. The standard error for each tooth is plus or minus 0.7 picocuries. Thus, there is a 95% chance that the "actual" amount of Sr-90 in a tooth with a ratio of 6.00 is between 4.60 and 7.40 (plus or minus twice the standard error). Obviously, when using large numbers of teeth, the error for the average level becomes much smaller.

     

    Ratios for some teeth are less reliable than for others. Generally, the ones with the lowest reliability are the smallest and/or most decayed, leaving little healthy enamel to be tested. RPHP assigns each tooth a "reliability (quench) factor", but includes them in all analyses of aggregate data.

     

  2. Change in Counter, Technique.

    3. After June 2000, when RPHP had Sr-90 results for 1335 teeth (including 206 from New Jersey), it made two upgrades to its testing procedures. First, it leased and began using a new machine, the 1220-003 Quantulus Ultra Low-Level Liquid Scintillation Spectrometer. Made by the Perkin-Elmer Company of Massachusetts, this new model is considered to be one of the most sophisticated counters in the field. Introduced in 1995, only about 15 to 20 are in use in the United States. (34)

     

    The new counter is located in the premises of REMS, Inc., and not in the basement of the University of Waterloo's science building, thus changing the nature of the radiation background. Also, the method of removing organic material from the teeth was changed by treating them with hydrogen peroxide prior to grinding them into powder. This proved to be more effective in allowing light produced in the liquid scintillation fluid by the beta particles emitted by the Sr-90 and its daughter product, Yttrium-90, to reach the photomultipliers, partly by shifting the spectrum of the light emitted by the scintillation fluid to some degree. As a result of these changes in the counter, its location, the nature of the background and the method of cleaning the teeth, the efficiency of detecting the very low radioactivity in single teeth was more than doubled, improving the quality of the data.

     

    Because the results from the two counters are each internally consistent but differ, the data from teeth measured before and after June 2000 cannot be merged. This report only covers those "newer" teeth, numbering 2089 at this writing.

     

  3. Comparisons for Consistency of Data.

RPHP set up a method to test the same teeth for Sr-90 in different laboratories, to assure that results produced by the REMS lab were consistent and accurate. The Perkin-Elmer Company staff recommended several users of the same model scintillation counter that RPHP was employing. RPHP selected Michael P. Neary, PhD, of the University of Georgia Center for Applied Isotope Studies for this test. Dr. Neary, an experienced radiochemist, operates three of the 15-20 units in the U.S., and was perhaps the first American to use them when he purchased them in the mid-1990s.

 

RPHP sent Dr. Sharma two batches of teeth to test. They contained 10 teeth each from persons born in St. Louis (from the original 1958-70 study mentioned earlier). One batch were 1954 births, and the other were 1959 births. Again, Drs. Sharma and Neary were blinded and had no information other than that they were baby teeth.

 

  1. Interlaboratory Consistency. Dr. Sharma dried teeth in the two batches and ground them into a powder. He tested Sr-90 levels for the 10 teeth from 1954 on the counter used in the RPHP tooth study. When he completed work, he sent the entire batch to Dr. Neary. Dr. Neary could only test the Sr-90 level of the dissolved solution of teeth, not the crushed powder, but this will not alter the results. The findings from each test of the 1954 teeth are as follows:

    2.  

     

     

     

    Table 4

    INTER-LAB COMPARISON, ST. LOUIS TEETH, 1954 BIRTHS

     

    Sr-90 Confidence

    Tester Level* Std. Error Interval+

    Sharma 1.77 +/- 0.31 1.15 - 2.39

    Neary 2.13 +/- 0.31 1.51 - 2.75

     

    * Average picocuries of Strontium-90 per gram of calcium at birth

     

    + Average Sr-90 level plus or minus two times the standard error, i.e. there is a 95% certainty that the actual value falls between these two values

     

    While there is some variation between each set of readings, there is substantial overlap between each confidence interval, therefore indicating that measurements are largely consistent between labs. It is clear that with a small sample (10 teeth), results will vary somewhat, which is why RPHP collected hundreds of teeth in the New Jersey before presenting data as anything more than preliminary.

     

  2. Intralaboratory Comparison. A second reliability test was performed by Dr. Sharma. Prior results from the St. Louis study indicated that average 1959 Sr-90 levels were considerably higher than those for 1954. Dr. Sharma split his two samples of 10 teeth each into two "sub-batches," and calculated Sr-90 levels separately. The following results were obtained:

 

Avg. % 1959 Confidence

Batch Sr-90* Over 1954 Std. Error Interval

#1 - 1954 1.66 +/- 0.27 1.12 - 2.20

- 1959 3.28 +98% +/- 0.36 2.56 - 4.00

 

#2 - 1954 1.77 +/- 0.31 1.15 - 2.39

-1959 3.36 +90% +/- 0.37 2.64 - 4.10

 

* Average picocuries of Strontium-90 per gram of calcium at birth

 

In the two tests, the excess of 1959 averages are slightly less than double that of 1954 (98% and 90%). Confidence levels do not overlap, meaning it is very likely the "true" values of the 1959 results exceed those for 1954. Thus, the RPHP results are also largely consistent with those found in the St. Louis study in the 1960s.

 

  1. Do Sr-90 Levels Represent Current or Past Emissions?

Some have suggested that the Sr-90 detected in the RPHP study may not represent new emissions from nuclear reactors, but instead represent leftover fallout from atmospheric atomic bomb tests in Nevada from 1951-62. Large-scale atmospheric testing ended in 1963, and the last above-ground test worldwide took place in China in 1980. Even U.S. underground tests ended in 1992. There are no other sources of Sr-90 other than bomb tests or reactor emissions.

 

There are numerous reasons why the great majority of Sr-90 detected in baby teeth of today's children represents emissions from nuclear reactors, not old bomb test fallout.

 

  1. Physical/Biological Half-Life. A fetus takes up Sr-90 in its tooth buds from the mother's bone stores and from the mother's diet (delivered to the fetus through the placenta) during pregnancy. During early infancy, Sr-90 is taken up from the diet, whether the baby is bottle-fed or breast-fed.

    2.  

    The biological half-life of Sr-90 in the body is about two years for children and 5-10 years for adults, before transforming into its daughter product Yttrium-90. Thus, the bones of the mothers of tooth donors (many of whom were at least 25 at delivery) should have little Sr-90 remaining in their bone stores by now.

     

    The physical half-life of Sr-90 is about 28.7 years. But Sr-90 that rained into reservoirs (drinking water) 40-50 years ago has long sunk into the sediment, because strontium is heavier than water. Similarly, Sr-90 that rained onto grass which cows graze on has long ago penetrated into the soil, or run off with excess water.

     

    Thus, it is logical that little Sr-90 from 1950s and 1960s bomb tests remains in mother's bodies or in the environment, and most of the current Sr-90 represents emissions from nuclear reactors.

     

  2. Sr-90 in Bone, Teeth Leveling or Rising. There is a precedent for reactor emissions causing rises in Sr-90. In southern Germany, 280 baby teeth from children born before and after the Chernobyl accident were analyzed. The change from 0.81 to 7.56 picocuries of Sr-90 per gram calcium, nearly a ten-fold increase, was observed for children born 1983-85 and 1987. (24)

    3.  

    The St. Louis baby tooth study also examined Sr-90 levels in the mandibles (jaw bone) of dead fetuses. Similar to baby teeth, a large increase was observed in the early 1960s, during the height of atmospheric bomb testing. However, after large-scale testing ended following the Test Ban Treaty, average Sr-90 levels fell by about half from 1964-69. No further data are available because federal government support for the study ceased in 1970. (23)

     

    In the late 1960s, only a half-dozen small nuclear reactors were in operation, and underground bomb tests emitted considerably less radiation into the atmosphere than did above-ground tests. If the 1964-69 trend had continued, about 97-99% less Sr-90 should now be present in the body at birth, or less than 0.5 picocuries. But RPHP found otherwise. In the first 1335 teeth (using the "old" counter and technique), the average Sr-90 level fell nearly in half from 1974-76 to 1983-85. For persons born since 1985, however, there was a slight increase. Using the new technique/counter, the rapid Sr-90 decline stopped at the same time, and has actually increased 48.5% from 1986-89 to 1994-97 (Table 5 and Figure 1).

     

    There can be no explanation for this reversal other than an increase in a current source of radioactivity, and this must be nuclear reactors. Since the early 1980s, the number of operating reactors has risen from about 70 to just over 100. Moreover, plants are closed less frequently for inspections, maintenance, and repairs, and the number of gigawatt-hours of electricity produced by these reactors tripled during this time. (3)

     

    Table 5

    AVERAGE SR-90 CONCENTRATION, BY BIRTH YEAR, U.S.

    TEETH TESTED AFTER JUNE 2000

     

    Birth Yr No. Teeth Avg. Sr-90*

    1954-57 6 5.15

    1958-61 8 8.94

    1962-65 8 9.48

    1966-69 17 7.35

    1970-73 38 6.01

    1974-77 38 5.69

    1978-81 78 3.79

    1982-85 172 3.78

    1986-89 532 2.95

    1990-93 836 3.56

    1994-97 346 4.38

     

    % Change, 1986-89 to 1994-97 +48.5%

     

    Note: Most teeth are from states of CA, CT, FL, NJ, NY, and PA

     

    * Average picocuries of Strontium-90 per gram of calcium at birth

     

  3. Philippino Sr-90 Teeth Considerably Lower. RPHP collected several dozen teeth from persons born in the Philippine Islands. No nuclear reactor (for weapons, power, or research) has ever operated in this nation. It may have received fallout from Chinese atmospheric bomb tests, but these were many fewer of these than U.S. tests, and they ended in 1980. Thus, if emissions from reactors are contributing to current Sr-90 levels, Philippino teeth should contain less of this chemical than American teeth.

    4.  

    Thirteen (13) teeth of children born in 1991 and 1992 (9 and 4, respectively), were tested. The average Sr-90 concentration at birth was 2.04 (using the new technique/counter). The average for teeth of American children born those years was 3.44, making Philippino teeth about 41% lower than U.S. teeth. Again, reactors appear to be a major source of current Sr-90 levels (note that some Sr-90 may exist in Philippino teeth due to imported food products from affected areas), and that there is an error factor when using only 13 teeth.

     

  4. California Sr-90 Teeth Rise After Reactor Opening. RPHP collected 34 teeth from San Luis Obispo County CA, the location of the Diablo Canyon 1 and 2 reactors, which started operations in 1984 and 1985. The average Sr-90 concentration for children born after the reactors opened was 49.6% greater than those born before (average of 2.02 vs. 1.35), suggesting that emissions from the new reactors accounted for this rise. The comparison used the "old" technique and machine.

    5.  

  5. Other Reports Indicate Current Rates Should Be Near Zero. One of the recent Sr-90 tooth studies mentioned earlier by Greek researchers contained a chart summarizing trends in Sr-90 in deciduous (baby) teeth from various European nations and the Soviet Union. The chart shows that, from a level of about 0.27 picocuries of Sr-90 per gram of calcium in 1951, a peak of 6.75 was reached in 1964, similar to the U.S. trend. By 1975, the average level had slumped to about 0.81 (three times the 1951 average) and was still declining. (25)

    6.  

    At three times the 1951 average, the 1975 U.S. Sr-90 level should have been about 0.6 (0.2 times three) picocuries Sr-90 per gram calcium. But the actual levels found by RPHP were 3.03 and 4.95 (8 and 12 teeth, respectively, using the old and new technique/method).

     

  6. Short-Lived Radioactive Chemicals Found In Local Eggshells. In 2001, a high school student from Rockland County NY presented an innovative idea for the Tooth Fairy Project. RPHP could not measure levels of short-lived radioactive chemicals in baby teeth, which now can only come from reactors. These include Strontium-89, with a physical half-life of 50 days and Barium-140, with a half-life of 13 days. By the time the child lost a baby tooth, at least five years after birth, the short-lived particles had disappeared.

 

The student's idea was to test chicken eggshells for short-lived radioactivity. She collected several local specimens soon after they were hatched, and rushed them to the REMS laboratory, which tested for Barium-140. These preliminary tests found several picocuries of Ba-140, which because of its rapid half-life could only have come from a nuclear reactor, probably the nearby Indian Point facility.

 

STUDY RESULTS

 

  1. Results by State.

    2. A total of 271 New Jersey teeth were tested under the "new" method and technique. Of these, 244 were from persons born after 1979, in whom most of the in-body Sr-90 was from current sources, not leftover fallout from Nevada bomb tests. Teeth from the 27 New Jersey residents born before 1980 had an average Sr-90 concentration of 7.04, more than double the post-1979 average of 3.39. Thus, the 244 post-1979 births will be the focus of this analysis.

     

    Table 6 displays the state-by-state Sr-90 averages for the states with at least 130 teeth (no other state contributed more than 34). New Jersey's average of 3.39 is slightly less than the overall study average of 3.56.

     

    Table 6

    AVERAGE SR-90 CONCENTRATION*

    BY STATE, PERSONS BORN AFTER 1979

     

    State Teeth Avg pCi Sr90*

    PA 130 4.16

     

    NY 534 3.74

     

    FL 471 3.50

     

    Other 417 3.50

     

    NJ 244 3.39

     

    CA 138 2.92

     

    TOTAL 1934 3.56

     

    * Average picocuries of Strontium-90 per gram of calcium at birth

     

     

  2. Results by County.

    3. Among the 244 teeth from New Jersey, 70% were from Ocean (148) and Monmouth (21) counties. Persons living near the Oyster Creek reactor were more likely to show interest in the study and to contribute teeth.

     

    Table 7 divides New Jersey tooth results into three geographic portions: Ocean and Monmouth counties; the six counties in northeast New Jersey (Bergen, Essex, Hudson, Middlesex, Passaic, and Union); and the remainder of the state. The average Sr-90 level for Ocean/Monmouth and the northeast corridor were virtually identical (3.47 and 3.51). The northeast corridor lies between the Oyster Creek and Indian Point nuclear plants. However, baby teeth from the remainder of the state had an average 21% lower (2.86).

     

    Table 7 also shows that within Ocean County, there is little variation in Sr-90 averages. Nearly half of the 148 teeth tested from the county were from the nearby towns of Toms River (39) and Brick (32). The average Sr-90 in these towns were nearly identical (3.52 and 3.51), and just barely higher than other towns in the county (3.38).

     

    Table 7

    AVERAGE SR-90 CONCENTRATION* IN NEW JERSEY

    BY COUNTY AND SUB-COUNTY, PERSONS BORN AFTER 1979

     

    County Teeth Avg pCi Sr90*

    Ocean, Monmouth 169 3.47

     

    Other New Jersey 75 3.22

    (Six Northeast Counties 41 3.51)

    (Other 13 Counties 34 2.86)

     

    TOTAL 244 3.39

     

     

     

    Area of Ocean County

    Toms River 39 3.52

     

    Brick 32 3.51

     

    Other Ocean County 77 3.38

     

    TOTAL 148 3.45

     

    * Average picocuries of Strontium-90 per gram of calcium at birth

     

    Notes: The number of teeth by county in New Jersey include:

    Atlantic 3 Gloucester 1 Ocean 148

    Bergen 10 Hudson 7 Passaic 1

    Burlington 3 Hunterdon 1 Salem 0

    Camden 2 Mercer 1 Somerset 1

    Cape May 15 Middlesex 8 Sussex 0

    Cumberland 1 Monmouth 21 Union 3

    Essex 12 Morris 3 Warren 0

     

    Toms River includes zip code 08753. Brick includes zip codes 08723, 08724.

     

  3. Results Over Time, by State and Ocean County.

    4. This report noted earlier that since the mid-1960s, average Sr-90 levels had steadily fallen nationwide, but rose about 50% from the late 1980s to the late 1990s. This reversal occurred in New Jersey as well. Table 8 and Figure 2 show the trend ending for persons born 1986-89, then rising until the latest period, 1994-97. The rise between the two periods was 36.6% in the entire state, and 49.8% for Ocean and Monmouth Counties. Preliminary results, using the old counter and presented in April 2001, showed the same trend (see Appendix 2).

     

    Table 8

    TRENDS IN AVERAGE STRONTIUM-90* LEVELS

    SINCE 1978, NEW JERSEY AND OCEAN/MONMOUTH COUNTIES

     

    Total New Jersey Ocean/Monmouth

    Birth Yr. Teeth Avg. Sr-90* Teeth Avg. Sr-90*

    1978-81 11 4.77 9 4.72

    1982-85 19 3.17 13 4.06

    1986-89 71 2.85 44 2.51

    1990-93 109 3.58 76 3.78

    1994-97 39 3.89 31 3.76

     

    % Ch, 1986-89 to 1994-97 +36.6% +49.8%

     

    * Average picocuries of Strontium-90 per gram of calcium at birth

     

     

  4. Birthweight.

    5. RPHP asked parents donating teeth to provide the child's birth weight to assess if high- or low-weight babies have unusual levels of Sr-90. Elevated Sr-90 (and other radioactivity) levels may impair fetal development, possibly leading to underweight births (at or under 5 pounds 8 ounces); and many medical journal articles have tied unusually high birth weight (at or over 8 pounds 12 ounces) to a high risk of childhood cancer.

     

    In Ocean and Monmouth Counties, 23 of 169 children were classified as high-weight; their average Sr-90 level is 3.95 pCi Sr-90/g Ca, or 15.5% higher than those of normal weight (3.42). There were also five born at low weight, but their average Sr-90 level was 2.57, well below the two-county average of 3.47. Thus, no conclusive evidence exists to tie high Sr-90 levels in teeth to high or low birth weight.

     

  5. Strontium-90 and Childhood Cancer Trends.

This report has already discussed rising childhood cancer rates and rising Sr-90 rates in Ocean and Monmouth Counties. The logical question is whether there is a statistical linkage between the two. In a previous report, RPHP showed that trends in average Sr-90 levels and childhood cancer incidence (rate of new cases) in Suffolk County, Long Island were nearly identical over a 10-year period, covering hundreds of baby teeth and cancer cases. (28)

 

The trends in Sr-90 average and childhood cancer incidence in Ocean and Monmouth Counties were compared using three-year groups (1983-85, 1984-86, etc.) instead of single years to enlarge the number of cases/teeth, making the comparison more meaningful. In addition, a "lag period" between exposure and diagnosis was tested. If Sr-90 increases in a given year, one would investigate any increase in childhood cancer not necessarily the same year, but more likely several years in the future. For example, the Chernobyl accident took place in 1986, but the large rise in childhood thyroid cancer did not take place until 1990. In the New Jersey tooth study, a five-year latency proved to be the best match.

 

Table 9 and Figure 3 show that the trends in Sr-90 and cancer incidence in Ocean and Monmouth County children under age 10 look very much alike over a 14-year period. In other words, when Sr-90 increased, there was an increase in cancer incidence 0-9 five years later; decreased were followed by subsequent decreases. This finding is very similar to that in Suffolk County, Long Island; and since it involves 167 baby teeth and 434 cancer cases, it suggests a statistical link between radiation and cancer in Ocean and Monmouth County children.

 

Table 9

TRENDS IN SR-90 AND CANCER INCIDENCE 0-9

OCEAN AND MONMOUTH (NJ) COUNTIES

FIVE-YEAR LATENCY PERIOD

 

Avg. pCi Sr-90/g Ca Cancer Incidence

Birth Year at Birth (No. Teeth) Diag. Year Rate/100,000 (Cases)

1980-82 3.19 (10) 1985-87 19.24 (71)

1981-83 3.31 (11) 1986-88 20.51 (78)

1982-84 3.41 ( 9) 1987-89 21.79 (85)

1983-85 4.96 ( 8) 1988-90 21.92 (87)

1984-86 4.34 (11) 1989-91 21.28 (86)

1985-87 3.08 (23) 1990-92 19.15 (79)

1986-88 2.69 (30) 1991-93 18.17 (77)

1987-89 2.38 (38) 1992-94 16.53 (72)

1988-90 2.83 (41) 1993-95 16.57 (74)

1989-91 3.35 (50) 1994-96 19.98 (91)

1990-92 3.80 (52) 1995-97 20.18 (93)

1991-93 3.89 (60) 1996-98 20.49 (95)

1992-94 3.62 (60) 1997-99 16.61 (77)

1993-95 3.79 (53) 1998-00 17.40 (81)

 

Sources: Radiation and Public Health Project (Sr-90) and New Jersey State Cancer Registry (cancer).

 

 

DISCUSSION/IMPLICATIONS

 

The RPHP study of Sr-90 concentrations in baby teeth of children near nuclear reactors is a landmark scientific effort, the first program of testing in-body levels of humans living near reactors. In New Jersey, a combination of the Oyster Creek reactor emitting the largest amount of radioactivity of all 103 U.S. reactors, plus high local childhood/adolescent cancer rates made the Ocean/Monmouth County area a logical one to examine current trends and patterns of Sr-90.

 

The study tested 271 teeth from New Jersey, focusing on 244 born after 1979 (whose in-body Sr-90 is mostly from a current source, not old Nevada bomb test fallout). Of these, 148 were from Ocean County, and another 21 from Monmouth County. The New Jersey state average Sr-90 was slightly below the national mark, with the highest levels in Ocean/Monmouth and the six northeast counties in the state. Thus, proximity to a nuclear reactor may be one factor in elevated Sr-90, with a downwind location being another (the prevailing wind near Oyster Creek blows from the south).

 

After a long period of declining Sr-90 after the 1963 treaty ending large-scale above-ground bomb tests, averages rose in Ocean/Monmouth, New Jersey, and other states after the late 1980s. This steady and consistent increase, documented in over 2000 teeth, must be a result of a current source of radioactivity. The last atomic bomb test underground in Nevada occurred in September 1992. The only current sources of Sr-90 (besides power reactors) are waste (which is stored and not active in the food chain), nuclear-powered submarines (again, not in the food chain), and research reactors (there are only a few, they are small, and their number is declining). Thus, it is logical to conclude that nuclear power reactors are likely to be the principal source of the most recent Sr-90 rise, especially as reactors age and are in operation a greater percentage of the time.

 

Perhaps the most important finding of the study is that in Ocean and Monmouth Counties, the trends in average Sr-90 levels and in childhood cancer are very similar, as they were in Suffolk County, New York. This suggests a statistical link exists between Sr-90 (as a proxy for the 100-plus radioactive chemicals produced only by nuclear reactors like Oyster Creek) and human disease. Effects are usually detected first in children, but also in adults after a longer lag period of a decade or more after exposure.

 

There are several parties who could make use of the information in this report:

 

  1. Scientists. RPHP has already published three medical journal articles on the tooth study, and has submitted a fourth containing this updated information, which can enhance the current understanding of radiation health risks.

    2.  

  2. Regulators. The U.S. Nuclear Regulatory Commission and/or the radiation regulatory body of the New Jersey Department of Health can use the information to institute a program measuring in-body radiation levels, for the first time since reactors began operations in 1957.

    3.  

  3. Researchers. Epidemiological and clinical studies of the effects of radioactive reactor emissions entering the body have been virtually non-existent. With reactors aging and operating a larger proportion of the time, and with rates of diseases such as childhood and breast cancer rising, researchers can examine radiation exposure as one potential factor in these trends.

    4.  

  4. Policy Makers. Elected officials and regulators can use information to establish policies to reduce radiation exposure, a preventive health measure that can lower future cancer rates.

    5.  

  5. The Public. Members of the general population concerned about environmental threats can understand these data, assisted by media reports and advocacy work by environmental groups, to encourage policy makers to reduce radiation exposure.

 

APPENDIX 1

DETERMINATION OF STRONTIUM-90 TO CALCIUM RATIO

 

Strontium-90 in dedicuous teeth was determined under the direction of Hari D. Sharma, Professor Emeritus of Radiochemistry and president of REMS, Inc., Waterloo, Ontario, Canada. Employing a 1220-003 Quantulus Ultra Low-Level Liquid Scintillation Spectrometer manufactured by the Perkin Elmer Company in Massachusetts, Dr. Sharma followed the following procedure.

 

Water-washed teeth were treated with 30 per cent hydrogen peroxide for a period of 24 hours to ensure that organic material adhering to teeth was oxidized. Teeth were then scrubbed with a hard brush for removing oxidized organic material and the fillings. Teeth are then dried at 110 degrees celsius (centigrade) and then ground to a fine powder (ball mill). It is very important to remove any filling because if left behind inside a tooth, it tends to give colored solution or dissolution in a mineral acid. The presence of colored solution reduces the efficiency of counting.

 

Approximately 0.1 gram of the powder is weighed in a vial, then digested for a few hours with 0.5 milliliter of concentrated nitric acid along with solutions containing 5 milligrams of Sr2+ and 2 milligrams of Y3+ carriers at about 110 degrees C on a sand bath. The solution is not evaporated to dryness. The digested powder is transferred to a centrifuge tube by rinsing with tritium-free water. Carbonates of Sr, Y, and Ca are precipitated by addition of a saturated solution of sodium carbonate, then centrifuged. The carbonates are repeatedly washed with a dilute solution of sodium carbonate to remove any coloration from the precipitate. The precipitate is dissolved in hydrochloric acid, and the pH is adjusted to 1.5 to 2 to make a volume of 2 milliliters, of which 0.1 milliliter is set aside for the determination of calcium. The remaining 1.9 milliliters are mixed with 9.1 milliliters of scintillation cocktail Ultima Gold AB, supplied by Packard Bioscience BV in a special vial for counting. A blank with appropriate amounts of Ca2+, Sr2+, and Y+3 is prepared for recording the background.

 

The activity in the vial with the dissolved tooth is counted four times, 100 minutes each time, for a total of 400 minutes, with the scintillation spectrometer. The machine has special features so that the background count-rate in the 400 to 1,000 channels is 2.25 +/- 0.02 counts per minute. The background has been counted for over 5,000 minutes so that the error associated with the background measurement is about 1 percent. The overall uncertainty or one sigma associated with the measurement of Sr-90 per gram of calcium is +/- 0.7 picocuries per gram of calcium

 

The efficiency of counting was established using a calibrated solution of Sr-90/Y-90 obtained from the National Institute of Standards and Technology, using the following procedure. The calibrated solution is diluted in water containing a few milligrams of Sr2+ solution, and the count-rate from an aliquot of the solution is recorded in channel numbers ranging from 400 to 1,000 in order to determine the counting efficiency for the beta particles emitted by Sr-90 and Y-90. It is ensured that the Y-90 is in secular equilibrium with its parent Sr-90 in the solution. The counting efficiency was found to be 1.67 counts per decay of Sr-90 with 1.9 milliliters of Sr-90/Y-90 solution with 25 milligrams of Ca2+, 5 milligrams of Sr2+, 2 milligrams of Y3+, and 9.1 milliliters of the scintillation cocktail.

 

The calcium content was determined by using an Inductively Coupled Plasma instrument. The analysis is provided by the University of Waterloo laboratories.

 

APPENDIX 2

TRENDS IN AVERAGE STRONTIUM-90* LEVELS

SINCE 1978, NEW JERSEY

OLD AND NEW COUNTER/METHODS

 

 

 

New Counter/Method Old Counter/Method

Birth Yr. Teeth Avg. Sr-90* Teeth Avg. Sr-90*

1978-81 11 4.77 9 1.53

1982-85 19 3.17 25 1.44

1986-89 71 2.85 85 1.27

1990-93 109 3.58 66 1.56

1994-97 39 3.89 2 1.93

 

% Ch, 1986-89 to 1994-97 +36.6% +52.0%

(not significant due

to only 2 teeth, 1994-97)

 

* Average picocuries of Strontium-90 per gram of calcium at birth

 

Results from both counters and techniques show a decline until 1986-89, and an increase until 1994-97, the latest data available.

 

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