National Academies Press: OpenBook
« Previous: Toxicity and Related Data on Selected Cadmium Compounds
Suggested Citation:"Exposure Assessment." National Research Council. 1997. Toxicologic Assessment of the Army's Zinc Cadmium Sulfide Dispersion Tests. Washington, DC: The National Academies Press. doi: 10.17226/5739.
×

5
EXPOSURE ASSESSMENT

THIS CHAPTER CONTAINS the subcommittee's exposure assessment for zinc cadmium sulfide (ZnCdS) and cadmium.

ZINC CADMIUM SULFIDE

The subcommittee reviewed the Army's sampling and analytic methods for assessing exposures to ZnCdS and the Army's documents on exposure to ZnCdS in various locations. The Army measured the concentration of ZnCdS particles in its dispersion studies with impingement and filtration methods. The methods are described in Appendix F. The subcommittee concludes that those are accurate and appropriate methods for measuring ZnCdS.

The subcommittee also reviewed the Army's documents and estimated the concentrations and potential exposures (time-integrated concentrations) of ZnCdS that were achieved during the use of the compound in the Army's air dispersion tests. Table 5-1 provides information on location, dates, numbers, and quantities of ZnCdS releases. It also provides the maximum concentrations and exposure doses (concentration x time). The

Suggested Citation:"Exposure Assessment." National Research Council. 1997. Toxicologic Assessment of the Army's Zinc Cadmium Sulfide Dispersion Tests. Washington, DC: The National Academies Press. doi: 10.17226/5739.
×

TABLE 5-1 Exposure Data on ZnCdS Dispersion Tests

 

 

 

 

 

 

 

Populated Areas

 

 

 

 

 

 

 

Total Quantity of ZnCdS, kg

Max. Exp. to ZnCdS, µg-min/m3

Max. Conc. of ZnCdS, µg/m3

Cadmium inhalation intake, µg

Ref.

Place

Name

Start Date

End Date

No. of Releases

Approximate area affected, sq. miles

Releases not at Dugway Proving Ground

2

Camp Cooke Calif.

DEW 1

1955

 

39

2.3

<173

<7

<0.4

 

 

 

 

 

 

<10

<10

 

8

N. Carolina, S. Carolina, Georgia,

 

03/26/52

04/21/52

5

630

98

0.34

0.3

 

 

 

 

 

 

< 100,000

< 10,000

 

13

Corpus Christie, Tex.

WINDSOC

08/13/59

02/22/60

13

~1,600

NA

NA

NA

 

 

 

 

 

 

< 100,000

< 10,000

 

16

Oklahoma

 

06/04/62

06/16/62

9

204

39

0.75

0.1

 

 

 

 

 

 

 

< 1,000

< 1,000

 

16

Texas

 

06/24/62

06/29/69

9

204

36

0.82

<0.1

 

 

 

 

 

 

 

< 1,000

< 1,000

 

16

Washington

 

10/02/62

10/21/62

9

204

6.7

0.3

<0.1

 

 

 

 

 

 

 

< 1,000

< 1,000

 

16

Nevada

 

10/31/62

11/05/62

8

181

23

1.6

<0.1

 

 

 

 

 

 

 

< 1,000

< 1,000

 

17 & 43

St. Louis

 

05/27/63

03/17/65

42

984

7,400

40

19.2

 

 

 

 

 

 

<10

<10

 

19

Chippewa National Forest, Minn.

 

01/25/64

08/07/64

24

330

1,620

3

4.2

 

 

 

 

 

 

<1,000

< 1,000

 

20

San Francisco

 

03/25/64

04/23/67

18

27.75

< 1,900

<170

4.9

 

 

 

 

 

 

<10

<1

 

22

Fort Wayne, Ind.

 

02/02/64

02/04/66

75

~1,650

410

<20

1.1

 

 

 

 

 

 

< 1,000

< 1,000

 

24

Oceanside, Calif.

Onshore Offshore releases

06/23/67

07/17/67

45

237

694

1,741

1.8

 

 

 

 

 

<1

<1

 

 

 

 

 

 

149

1.3

0.4

 

 

 

 

 

< 1,000

< 1,000

 

27

Pack Forest, Wash.

 

10/15/68

09/05/69

33

1.7

 

 

?

28

Green Brier Swamp, Md.

MATE

08/01/69

10/29/69

111

2.7

<42

-0.03

<0.1

 

 

 

 

 

 

< 1

< 1

 

Suggested Citation:"Exposure Assessment." National Research Council. 1997. Toxicologic Assessment of the Army's Zinc Cadmium Sulfide Dispersion Tests. Washington, DC: The National Academies Press. doi: 10.17226/5739.
×

 

 

 

 

 

 

 

Populated Areas

 

 

 

 

 

 

No. of Releases

Total Quantity of ZnCdS, kg

Max. Exp. to ZnCdS, µg-min/m3

Max. Conc. of ZnCdS, µg/m3

Cadmium inhalation intake, µg

Ref.

Place

Name

Start Date

End Date

Approximate area affected, sq. miles

30

Camp Detrick, Md.

SELTZER

02/18/53

02/24/53

4

0.022

71

9

0.2

 

 

 

 

 

 

<10

<1

 

30

Biltmore Beach

WHITEHORSE

03/24/53

05/02/53

12

9.7

150,000

4,800

390

 

 

 

 

 

 

<0.1

<0.1

 

33

Dallas

 

04/01/61

08/31/61

37

 

NA

NA

NA

 

 

 

 

 

 

 

<1,000

<1,000

 

35

St. Louis

 

01/19/53

10/18/53

35

 

2,000

340

5.2

 

 

 

 

 

 

 

<10

<0.1

 

35

Minneapolis

 

05/20153

06/23/53

102

7.9

2,600

300

6.8

 

 

 

 

 

 

 

<10

<0.1

 

35

Winnipeg

 

07/09/53

08/01/53

36

5.8

5,600

1,000

14.5

 

 

 

 

 

 

 

<10

<0.1

 

36

Stanford University, Calif.

 

10/15/47

10/15/47

1

0.00083

5

2

<0.1

37

Palo Alto, Calif.

 

03/10/50

03/14/50

2

0.976

2.4

0.5

<0.1

 

 

 

 

 

 

<100

<100

 

37

San Francisco

 

10/20/50

10/27/50

6

22.44

436

15

1.1

 

 

 

 

 

 

<100

<100

 

41

Palo Alto, Calif.

 

01/26/62

11/16/62

28

1.4

1,676

?

4.4

 

 

 

 

 

 

<0.1

<0.1

 

 

 

 

Releases at Dugway Proving Ground

 

 

 

3

Dugway

 

05/04/53

06/03/53

2

5.534

 

 

 

4

Dugway

 

01/21/54

03/14/54

4

0.0348

 

 

 

6

Dugway

 

05/18/55

05/18/55

2

0.0424

 

 

 

18

Dugway

 

05/17/63

08/15/63

9

29.6

 

 

 

29

Dugway

GOOF

08/23/55

11/01/55

5

0.8

<409

 

<1.1

31

Dugway

 

04/03/58

04/22/58

4

0.0534

 

 

 

32

Dugway

 

02/70 to

 

6

0.21

 

 

 

 

 

 

03/70

 

 

 

 

 

 

37

Dugway

 

07/01/50

08/04/50

9

8.244

0.03

 

<0.1

Suggested Citation:"Exposure Assessment." National Research Council. 1997. Toxicologic Assessment of the Army's Zinc Cadmium Sulfide Dispersion Tests. Washington, DC: The National Academies Press. doi: 10.17226/5739.
×

four highest ZnCdS exposures were in Minneapolis (44 µg), Winnipeg (93 µg), St. Louis (156 µg), and Biltmore Beach, FL (2,500 µg). To obtain the exposure to cadmium, the maximal exposure of ZnCdS (expressed as µg-min/m3 as shown in Table 5-1) is multiplied by 0.0166 m3/min (the volume of air inhaled by an active person in 1 min). The product is then multiplied by 0.156 (the mass fraction of cadmium in ZnCdS). For example, the corresponding amounts of cadmium in the ZnCdS doses are 6.8 µg in Minnesota, 14.5 µg in Winnipeg, 24.4 µg in St. Louis, and 390 µg in Biltmore Beach.

CADMIUM

The purpose of this section is to provide estimates of the magnitude of potential cadmium doses from human contact with cadmium compounds as a result of the dispersion of ZnCdS by the Army and to compare them with the estimated doses from environmental and industrial sources. In the United States, mean concentrations of cadmium in ambient air range from less than 0.001 µg/m3 in remote areas to 0.005-0.04 µg/m3 in urban areas (Davidson and others 1985; Elinder 1985; EPA 1981; Saltzman and others 1985). Atmospheric concentrations of cadmium are generally highest in the vicinity of cadmium-emitting industries, such as smelters, municipal incinerators, and fossil-fuel combustion facilities. Measurements of atmospheric cadmium up to 7 µg/m3 have been reported in these industrial types of areas in the United States (Schroeder and others 1987). Cadmium intake from air is estimated to be 0.1-0.8 µg per day in typical U.S. urban areas and less than 0.02 µg in rural areas.

Food is the largest potential source of cadmium exposure for the general population. There are several estimates of the daily adult intake of cadmium from food in the United States, but there is considerable variation among those estimates. Schroeder and Balassa (1961) reported a range of 4-60 µg and Nriagu (1981) a range of 38-92 µg, whereas estimated daily averages have been reported to be 30 µg (Gartrell and others 1986), 38 µg (Duggan and Corneliussen 1972), 50 µg (Duggan and Corneliussen 1972), 51 µg (Mahaffey and others 1975), and 92 µg (Murthy and others 1971). A more recent estimate based on a total diet

Suggested Citation:"Exposure Assessment." National Research Council. 1997. Toxicologic Assessment of the Army's Zinc Cadmium Sulfide Dispersion Tests. Washington, DC: The National Academies Press. doi: 10.17226/5739.
×

study shows the daily dietary intake to be about 15 µg (Gunderson, 1995). Analysis of the earlier data shows that these discrepancies are probably due to different analytic methods. Cadmium contamination of food has been reduced over the years, presumably because of better technology. However, the cadmium contamination encountered in the 1950s and 1960s, when the Army's dispersion tests were conducted, are more relevant for risk assessment. On the basis of the U.S. data and data from other industrial nations in the Northern Hemisphere, the subcommittee believes that the daily cadmium intake from food ranges from 10 to 60 µg.

Except in the vicinity of cadmium-emitting industries, the cadmium in most U.S. drinking- water supplies is less than 1 µg/L (Konz and Walker 1979). However, concentrations of up to 10 µg/L have been reported in some water supplies (EPA 1981). Thus, daily cadmium intake from drinking water is about 2-20 µg, assuming that a person drinks 2 L of water per day.

Cigarettes are also an important source of cadmium exposure. The amount of cadmium that can be inhaled from smoking one cigarette is 0.10.2 µg (Elinder and others 1983; Friberg and others 1974). Thus, it can be estimated that someone smoking one pack per day will take in 2-4 µg of cadmium per day. Environmental tobacco smoke or passive smoking is another source of human exposure to cadmium. It has been reported that the amount of cadmium (presumably as CdO) released in the mainstream smoke (the smoke that the smoker inhales) from smoking one cigarette is about 100 mg and the cadmium released in the sidestream smoke (the smoke that originates from the smoldering end of a cigarette in between puffs) is about 720 mg (NRC 1986; DHHS 1986; EPA 1992). The cigarette-smoker is subjected to the sidestream as is anyone near the smoker while the cigarette is burning. The amount of cadmium inhaled from passive smoking depends on several factors, such as number of cigarettes smoked, ventilation, dilution factor (e.g., size of the room), and duration of exposure.

Thus, the total daily human cadmium intake in industrial countries from environmental and industrial sources is 12-84 µg/d for an adult. For a 70-kg person, that corresponds to a potential intake of 0.2-1.2 µg/kg per day. Figure 5-1 shows the typical ranges of daily cadmium intake by exposure pathway. Food products and water contribute almost all the typical daily

Suggested Citation:"Exposure Assessment." National Research Council. 1997. Toxicologic Assessment of the Army's Zinc Cadmium Sulfide Dispersion Tests. Washington, DC: The National Academies Press. doi: 10.17226/5739.
×

FIGURE 5-1. Typical ranges of daily cadmium intake by exposure pathway.

human exposure; inhalation contributes a very small fraction. Not all the inhaled or ingested soluble cadmium is absorbed into the body. The subcommittee used the information on water-soluble cadmium compounds as the worst case. Only 25-50% of the inhaled cadmium is absorbed by the

Suggested Citation:"Exposure Assessment." National Research Council. 1997. Toxicologic Assessment of the Army's Zinc Cadmium Sulfide Dispersion Tests. Washington, DC: The National Academies Press. doi: 10.17226/5739.
×

lungs (Elinder and others 1976; Friberg and others 1986; Henderson and others 1979), and only 5% of the ingested cadmium is absorbed in the gastrointestinal tract (ATSDR 1992; Friberg and others 1974; IARC 1993; Nriagu 1980). Figure 5-2 presents a comparison of typical daily and annual inhalation intake of cadmium in urban areas with the time-integrated (total) potential inhalation doses of cadmium in the form of ZnCdS in 19 locations where it was released.

To consider both direct inhalation exposures and indirect exposures (ingestion and through skin contact) in its risk assessment, the subcommittee developed potential dose ratios that relate the direct-inhalation potential dose to the indirect potential doses associated with the same air concentration. The ratios are developed in Appendix I and summarized in Table 5-2, and were used to develop the comparisons in Figure 5-2. The exposure of a population to a cloud of ZnCdS is expressed as the product of time and concentration with units of µg-h/m3. Because the concentration varies in time, we believe that the cumulative exposure-time product, rather than peak concentration, is the most appropriate way to express exposure. Because the population doses that result from this exposure accumulate by multiple pathways, we developed a dose-to-exposure ratio for each pathway. These ratios are shown in Table 5-2. The potential doses can be interpreted as follows. Consider the inhalation pathway, listed at the top of the table. The entry of 1 µg per µg-h/m3 of exposure means that someone exposed for 1 h to a concentration of 1 µg/m3 will get a cumulative dose of 1 µg. It also means that someone exposed to 0.5 µg/m3 for 2 h, which is equivalent to an exposure of 1 µg-h/m3, will receive the same dose, 1 µg. A similar approach applies to each table entry.

Appendix I provides a detailed analysis of sources of environmental and industrial exposure, transport and environmental fate, sinks (reservoirs) of cadmium, and exposure pathways.

Estimated average total daily intake from environmental and industrial exposures to cadmium from all media (soil, water, food, and air) in urban areas are greater than any daily exposures to cadmium resulting from the ZnCdS particles in the Army tests, with the exception of 1 test at Biltmore Beach, an isolated beach area in Florida. It should be noted that the cadmium intake directly from air (that is, via inhalation) contributes very little to total cadmium intake in urban and industrial areas. Although on the

Suggested Citation:"Exposure Assessment." National Research Council. 1997. Toxicologic Assessment of the Army's Zinc Cadmium Sulfide Dispersion Tests. Washington, DC: The National Academies Press. doi: 10.17226/5739.
×

FIGURE 5-2. Comparison of typical daily and annual inhalation cadmium intake in urban areas to the time-integrated (total) potential inhalation doses to cadmium in the form of ZnCdS in locations where ZnCdS was released.

Suggested Citation:"Exposure Assessment." National Research Council. 1997. Toxicologic Assessment of the Army's Zinc Cadmium Sulfide Dispersion Tests. Washington, DC: The National Academies Press. doi: 10.17226/5739.
×

days of the Army tests, the sites of the highest monitored ZnCdS concentrations had concentrations of airborne cadmium (in the form of ZnCdS) that were above the estimated urban average daily airborne cadmium in about half the test sites, these short-term high concentrations had minimal impact on indirect cadmium exposures (from water, food, and soil).

TABLE 5-2 Summary of Potential Dose Ratios for Direct and Indirect Exposure Pathways

Exposure Pathway

Direct or Indirect Contact with Air

Potential Dose Ratio, µg/((µg-h)/m3) Cumulative Air Exposure

Inhalation

Direct

1.0

Inhalation of resuspended soil outdoors

Indirect

0.0005 to 0.002

Dermal contact with and ingestion of house dust

Indirect

2.5 to 5

Inhalation of resuspended house dust

Indirect

≈0.12

Deposition onto vegetation in home gardens

Indirect

2.2

Deposition onto surface drinking water supplies

Indirect

0.24 to 0.8

CONCLUSIONS

The subcommittee concludes that the four highest potential inhalation doses of ZnCdS that humans were exposed to during the Army's dispersion tests occurred in Minneapolis (44 µg), Winnipeg (93 µg), St. Louis (156 µg), and Biltmore Beach (2,500 µg). The corresponding amounts of cadmium in these doses are 6.8 µg in Minnesota, 14.5 µg in Winnipeg, 24.4 µg in St. Louis, and 390 µg in Biltmore Beach. On the basis of these estimates, the subcommittee concludes that exposure to cadmium from the dispersion tests (except for Biltmore Beach, FL, an unpopulated remote area at the time of the Army's tests) did not exceed the background expo-

Suggested Citation:"Exposure Assessment." National Research Council. 1997. Toxicologic Assessment of the Army's Zinc Cadmium Sulfide Dispersion Tests. Washington, DC: The National Academies Press. doi: 10.17226/5739.
×

sures encountered in urban areas. It should be noted that cadmium intake directly from air (that is, via inhalation) contributes very little to total cadmium intake in urban and industrial areas. Although, on the days of the Army tests, the sites of the highest monitored ZnCdS concentrations had concentrations of airborne cadmium (in the form of ZnCdS) that were above the estimated urban average daily airborne cadmium in about half the test sites, these short-term high concentrations had minimal impact on indirect cadmium exposures (from water, food, and soil).

Suggested Citation:"Exposure Assessment." National Research Council. 1997. Toxicologic Assessment of the Army's Zinc Cadmium Sulfide Dispersion Tests. Washington, DC: The National Academies Press. doi: 10.17226/5739.
×
Page 57
Suggested Citation:"Exposure Assessment." National Research Council. 1997. Toxicologic Assessment of the Army's Zinc Cadmium Sulfide Dispersion Tests. Washington, DC: The National Academies Press. doi: 10.17226/5739.
×
Page 58
Suggested Citation:"Exposure Assessment." National Research Council. 1997. Toxicologic Assessment of the Army's Zinc Cadmium Sulfide Dispersion Tests. Washington, DC: The National Academies Press. doi: 10.17226/5739.
×
Page 59
Suggested Citation:"Exposure Assessment." National Research Council. 1997. Toxicologic Assessment of the Army's Zinc Cadmium Sulfide Dispersion Tests. Washington, DC: The National Academies Press. doi: 10.17226/5739.
×
Page 60
Suggested Citation:"Exposure Assessment." National Research Council. 1997. Toxicologic Assessment of the Army's Zinc Cadmium Sulfide Dispersion Tests. Washington, DC: The National Academies Press. doi: 10.17226/5739.
×
Page 61
Suggested Citation:"Exposure Assessment." National Research Council. 1997. Toxicologic Assessment of the Army's Zinc Cadmium Sulfide Dispersion Tests. Washington, DC: The National Academies Press. doi: 10.17226/5739.
×
Page 62
Suggested Citation:"Exposure Assessment." National Research Council. 1997. Toxicologic Assessment of the Army's Zinc Cadmium Sulfide Dispersion Tests. Washington, DC: The National Academies Press. doi: 10.17226/5739.
×
Page 63
Suggested Citation:"Exposure Assessment." National Research Council. 1997. Toxicologic Assessment of the Army's Zinc Cadmium Sulfide Dispersion Tests. Washington, DC: The National Academies Press. doi: 10.17226/5739.
×
Page 64
Suggested Citation:"Exposure Assessment." National Research Council. 1997. Toxicologic Assessment of the Army's Zinc Cadmium Sulfide Dispersion Tests. Washington, DC: The National Academies Press. doi: 10.17226/5739.
×
Page 65
Suggested Citation:"Exposure Assessment." National Research Council. 1997. Toxicologic Assessment of the Army's Zinc Cadmium Sulfide Dispersion Tests. Washington, DC: The National Academies Press. doi: 10.17226/5739.
×
Page 66
Next: Risk Characterization of Exposures to Zinc Cadmium Sulfide »
Toxicologic Assessment of the Army's Zinc Cadmium Sulfide Dispersion Tests Get This Book
×
Buy Paperback | $80.00 Buy Ebook | $64.99
MyNAP members save 10% online.
Login or Register to save!
Download Free PDF

During the 1950s and 1960s, the U.S. Army conducted atmospheric dispersion tests in many American cities using fluorescent particles of zinc cadmium sulfide (ZnCdS) to develop and verify meteorological models to estimate the dispersal of aerosols. Upon learning of the tests, many citizens and some public health officials in the affected cities raised concerns about the health consequences of the tests. This book assesses the public health effects of the Army's tests, including the toxicity of ZnCdS, the toxicity of surrogate cadmium compounds, the environmental fate of ZnCdS, the extent of public exposures from the dispersion tests, and the risks of such exposures.

  1. ×

    Welcome to OpenBook!

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

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

    No Thanks Take a Tour »
  2. ×

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

    « Back Next »
  3. ×

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

    « Back Next »
  4. ×

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

    « Back Next »
  5. ×

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

    « Back Next »
  6. ×

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

    « Back Next »
  7. ×

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

    « Back Next »
  8. ×

    View our suggested citation for this chapter.

    « Back Next »
  9. ×

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

    « Back Next »
Stay Connected!