Radon monitoring in sites of economical importance in Jamaica

Applied Radiation and Isotopes 71 (2012) 96–101

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Radon monitoring in sites of economical importance in Jamaica C.N. Grant a, G.C. Lalor a, M. Balca´zar b,n a b

International Centre for Environmental and Nuclear Sciences, University of the West Indies, Mona Road, Kingston 7, Jamaica Instituto Nacional de Investigaciones Nucleares, Apartado Postal 18-1027, Mexico D.F. 11801, Mexico

H I G H L I G H T S c c c

Touristic caves of economical importance shown no radon risk for workers and visitors. Maximum permanence time due to abnormal radon is given for caves used by speleologist. Despite high Rn and U in soil in bauxite areas no risk is determined in houses.

a r t i c l e i n f o

a b s t r a c t

Available online 10 July 2012

The main task was to evaluate possible radon risk to the public and workers in four caves of economical importance. Green Grotto Cave is a large labyrinthine limestone cave, open to the tourism; kept Rn concentration in the range 30–40 Bq m  3. Xtabil a coral limestone sea cave is part of a beach resort resulted in very low radon concentration of 10 Bq m  3. Windsor is an intricate limestone cave system showed Rn concentration in the range 250–350 Bq m  3. Whereas the Oxford caves, is situated in a region of high radioactivity in soil due to the bauxite mines, reached a maximum of 2592 Bq m  3. & 2012 Elsevier Ltd. All rights reserved.

Keywords: Radon levels Caves Radon dose

1. Introduction An environmental radioactivity program carried out under a bilateral Mexican Jamaican agreement has been set in Jamaica, in order to assess the impact in three main areas of economical importance for Jamaica: Bauxite industry, Tourism and Agriculture. The major bauxite deposits are located in the parish of St. Elizabeth at the south west of the island where high radioactivity levels permitted the association of uranium, radium and consequently radon to the presence and prospecting of this mineral (Grant et al., 2001). St. Elizabeth is also one of the most important agricultural areas in Jamaica; in addition, inside and nearby this parish there are two types of caves, those regularly visited by tourists and the ones visited by speleologists. Therefore, it was decided to carry out a radon survey with two clear objectives; the first one being the determination of radon in four caves, two open to public tourism and two of speleologist interest for assessing the maximum occupation time in the caves. A second objective was to select some houses in St. Elizabeth

n

Corresponding author. Tel.: þ52 55 53297200x2673; fax: þ52 55 53297388. E-mail addresses: [email protected] (C.N. Grant), [email protected] (M. Balca´zar). 0969-8043/$ - see front matter & 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.apradiso.2012.07.007

parish together with others houses in a so called controlled site in Kinston, were the radioactivity levels are known to be low, to set for the first time radon indoor levels in Jamaica, which could help in a decision for more detailed studies. Further studies, not considered in this paper will consider radioactivity impact in agriculture activity. Radon is a radioactive gas originating as an intermediate product of 238U (222Rn), 235U (219Rn) and 232Th (220Rn) decay series. The most abundant Rn isotope, 222Rn, is released from soils and rocks depending on both the concentration and the distribution of its parent nuclide, 226Ra. Soil radon gas can also be transported by advective fluxes of geogases (CO2, H2O, H2S, CH4) from deeper tectonic activity, however, our initial findings in a previous survey in central Jamaica revealed levels of soil radon gas, some of which were significant, strongly correlated (r2 ¼0.86) with radium content of the soil (Grant et al., 2001), indicating that most of the soil gas radon was as a direct release from the soil. The health implications of radon inhalation have been well documented; it is considered by the World Health Organization, International Agency for Research on Cancer (WHOIARC) as a group 1 carcinogenic substance (Siemiatycki et al., 2005). In fact it has been estimated by United States Environmental Protection Agency (US EPA) that there are some 15,000–25,000 radon induced lung cancers annually in the US (Gates and Gunderson,

C.N. Grant et al. / Applied Radiation and Isotopes 71 (2012) 96–101

1992). National regulatory bodies in several countries have set action levels for indoor air. The ICRP has set action levels based upon an effective dose constraint of 10 mSv per year; assuming an equilibrium factor of 0.4 and 2000 h per year at work, this amounts to radon concentration of between 600 and 200 Bq m  3 for dwellings, with a corresponding range 1500–500 Bq m  3 (10–3 mSv) for the work place. (Ann. ICRP 23, 1993). The National Commission on Radiological Protection (NCRP) has set a level of 296 Bq m  3, the USEPA 148 Bq m  3, and the United Kingdom has set a level of 200 Bq m  3 for exposure at home, International Atomic Energy Agency (IAEA) set a value of 1000 Bq m  3 for work place exposure. Although exposure to radon is a complex problem, its restriction is often easily achieved once the problem has been identified. Simple remedial actions can often result in a significant reduction in exposures to ionizing radiation from this source.

97

cave is believed to have been started by joints and fractures that have been widened initially by fresh-water solution; their subsequent enlargement is believed to be the result of stopping and wave action more than by salt-water solution (Aley, 1964) In the elevated radioactivity area the Oxford Caves, located on the boarder of the parishes of Manchester and St. Elizabeth, is a fossil stream passage with a muddy floor, 10–15 m wide, 10–12 m high, and 765 m long that eventually ends in a mud choke (Aley, 1964). It has been reported that a great deal of damage has been done to this cave due to unsupervised visits and vandals. A second cave in an elevated radioactivity area is Windsor Cave, located in the parish of Trelawny, is one of the better-known caves on the island. This is a complexed limestone cave system almost 3 km in length and 20 m deep (Fincham A., 1997). It has seen much visitation over the years, has been mined for guano, and continues to experience tourism. Locations of homes, caves and offices in study and control areas are displayed in Fig. 1.

2. Sites of study The parish of St. Elizabeth, which has approximately 6% of the islands population, was selected to be the first study area because of the relatively high levels of radioactivity previously noted (Grant et al., 2001). The parish has an area of 1215 km2. The most extensive lithological unit in the parish is Tertiary White Limestone Formation, which covers over half the parish and occurs at elevations ranging from below sea level to over 762 m high. It forms the cap of the great Limestone Plateau of Jamaica, thickening with dips in some areas to the south. The St. Elizabeth Plains divides it into two main masses, the northern limestone region has been weathered to produce typical karst country with sinkholes, and dry valleys in abundance, the southern plateau region is heavily dissected by faults. Seven homes were selected within the study area, these included four homes (1, 2, 3, 4) of contemporary design made from concrete and steel having running water and tiled concrete floors, and three homes (A, B, C) constructed from Wattle and daub a woven latticework of wooden stakes called wattles daubed with a mixture of clay and sand and straw to create a structure. These homes carefully selected cover areas of low, medium and high soil radon concentrations. A control area selected for this study was the Liguanea Plains situated in the heart of Kingston Metropolitan area, Jamaica’s largest urban area with approximately 28% of the islands population. Previous studies (Grant et al., 2001) had identified the Kingston Metropolitan area as a region of low radioactivity. The Liguanea Plains, which is an old alluvial Holocene fan, consists of a thick series of sand, gravel and clay deposits bordered on the north and the east by predominantly Tertiary limestone hills. The offices (O1, O2) and control home one (C1) were located in the plain, control homes two (C2) and three (C3) were located on the surrounding northerly and easterly limestone hills respectively. Homes of Wattle and daub or buildings constructed in similar manor were not identified in the control area. Four caves were selected, two in regions of elevated radioactivity and two in a region low radioactivity but of great importance to the tourist industry. In the low radioactivity area the Green Grotto Cave, located in the parish of St. Anne at the north central part of Jamaica, is one of the Islands major tourist attraction, it consist of a 1525 m long labyrinthine limestone cave system and a subterranean lake (Fincham, 1997). The Green Grotto Cave was the first attraction of its kind in the world to be awarded Green Globe 21 Certification in 2003. Also in low radioactive area, the Xtabi cave in Negrils West End is part of a beach resort and restaurant; the cave is visited regularly by guest and visitors who use the cave as a route to seashore some 10 m below; this type of coral limestone sea

3. Experimental method 3.1. Radon measurements Two methods were used to assess radon concentration: an Alpha GUARD detector (Balca´zar, 2008), which is capable of measuring environmental radon concentration in situ every 10 min simultaneously with temperature and humidity was used for the measurements of the control homes, offices and caves. For the study area, which included many remote sites with difficult access, Kodak LR115 nuclear track etch detector film was used for home radon measurements. The measurement times were typically around 2 months; this ensured sufficient response on the film to provide an accurate radon reading. A detailed description of the measurement equipment and film processing has been given elsewhere (Grant et al., 2001). 3.2. Soil gas radon from radium Approximately 1/2 kg, was collected from each of the home sites in the study area and control area as well as soil from University Campus (Offices site), obvious pieces of rock and vegetation were removed, and the samples were placed in double strength labelled plastic bags, and returned to the laboratory. The bulk soil samples were then dry sieved through 2 mm and then through 150 mm nylon sieves. Each fraction was placed in Kraft paper bags, air dried at an ambient temperature of about 301C and subsequently oven-dried at approximately 45 1C for 12 h. The dried samples were then ground and homogenized in a Fritsch mortar-grinder and stored in polyethylene containers prior to analysis. The soil gas radon concentration was estimated using a previously established relationship between soil gas radon and radium soil content over white limestone lithologies in Jamaica (Grant et al., 2001). Approximately 35 g of sample were placed in a 30 cm3 plastic vial, the lid put firmly in place and sealed with paraffin film to prevent the leakage of radon gas. The vials were then left for a period of at least thirty days, for radon to reach secular equilibrium with radium, before measuring the activity of 214 Bi (Eg ¼609 keV and Eg ¼1.76 MeV) and 214Pb (Eg ¼351.9 keV). These isotopes are intense gamma emitters and rapidly reach secular equilibrium with radon. Each sample was counted for 50,000 s on a Canberra reverse electrode germanium photon detector with an efficiency of 15% at 1332.5 keV gamma rays. The detector was shielded with 0.5 cm of copper sheet surrounded by a 10 cm thickness of lead bricks. In addition to

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C.N. Grant et al. / Applied Radiation and Isotopes 71 (2012) 96–101

Fig. 1. Locations of homes, caves and offices in study and control areas.

the 214Bi, and 214Pb measurements, 226 Ra (Eg ¼ 186 keV) was also measured, however, the intensity of the associated gamma rays is considerably lower than those of 214Bi and 214Pb.

Soil gas radon vs House radon 110 100

3.3. Uranium content in soils

90

The U contents in soil samples were analyzed by comparative Neutron Activation Analysis (NAA) using the Jamaican SLOWPOKE 2 reactor and the same gamma ray spectroscopy system used for the equivalent uranium (eU) measurements. For NAA of U the 238 U(n, g, b) 239Np reaction was used for quantification, as a means of independent analysis, 235U was measured by delayed neutron counting (DNC) at the University of Alberta SLOWPOKE Facility using a BF3 detector (Duke, 1983; Amiel, 1962; Boulanger et al., 1975) all results were normalized by natural abundance to give total U.

80

House radon Bqm-3

y = 0.0011x + 1.8774 R2= 0.9255

Block Steel wattle control

70 60 50

y = -2.10-5x + 37.591 R2= 0.0006

40 30 20 10

4. Results and discussion 4.1. Radon in houses None of the houses measured during this survey in the high radioactive level at St. Elizabeth had radon concentrations that exceed any known set action level. The concentrations found for contemporarily designed homes ranged from 24 Bq m  3 to 38 Bq m  3 and is in good agreement with previously obtained results for conventional homes in Jamaica of 12 Bq m  3 to 37 Bq m  3 (Pinnock, 1999). The concentrations of radon in the homes of contemporary design are dependent upon the soil radon concentration, Fig. 2, but the effect is very weak. This was true for both the study and control areas. The majority of the soil gas radon in the white limestone regions of Jamaica emanates directly from the radium rich soil (Grant et al., 2001), it has also been reported that soil beneath an edifice can be a significant source of radon. The contribution of soil radium to the indoor radon concentration is a function of the emanating power of the soil and the tightness of the base structure (UNSCEAR, 1982), it has been estimated that a concrete floor with a 1% open crack spaces by volume would reduce radon

10

20

30

40

50

60

70

80

90

100

Soil radon kBqm-3 Fig. 2. Radon in homes as a function of soil radium and building type.

flux by 75% relative the case of a bare dirt floor, this would explain the weak dependence shown by homes with concrete tiled floors. Homes made from wattle and daub, all of which had wooden floorboards covering unpaved soil, exhibited a strong relationship between soil and indoor radon concentrations (r2 ¼0.97). The coefficients of the two shown linear fitted equations are indicative of the advection rates from the soil through floors in each type of building; however, for the wattle and daub houses this factor is compounded by the fact that the raw material for walls is inclusive of the local soil (Table 1). The radium content of the local soil and hence local raw materials used for the wattle is rich in radium. Typical 226Ra activity for conventional concrete is in the region of 30 Bq kg  1, based on measurements of the soil collected in the vicinity of

C.N. Grant et al. / Applied Radiation and Isotopes 71 (2012) 96–101

upon the emanation of the wattle material due to its radium content, it assumes a minimal and constant advection factor for the floor. The radon concentration was also calculated using the linear fit generated for the wattle and daub homes, Rn wattle and Daub. This approximation of the measured Rn, Rn wattle and Daub, is inclusive of the emanation of wattle material and advection through the wooden floorboards. The differences observed (Rn wattle and Daub–Rn conventional), Rn Advection, are due to the different advection rates for wooden floorboards covering unpaved soil and a concrete base. These results are in keeping with findings that advection through crawl spaces with bare unpaved soil is a major source of indoor radon (UNSCEAR, 1982). Measurement of indoor radon as a function of temperature and humidity in two control homes were also made. The radon concentration were generally quite low with a few radon peaks between 20 Bq m  3 and 35 Bq m  3 with average values of less than 10 Bq m  3, Temperature was around 30 1C and percentage humidity ranged from 60% to 70%, a negative correlation between radon concentration and humidity was determined (r ¼  0.25). For house 3 the Alpha GUARD detector was transported to the laboratory without being turned off, resulting in an increase of the Radon concentration at the end of corresponding graphs due to a higher radon concentration present in the laboratory (see Fig. 3b).

wattle and daub homes the content of local soil varied from 63 Bq kg  1 to 310 Bq kg  1. It has been previously shown that radon concentration in home constructed from conventional materials is half that of a home constructed from red mud, a bauxite waste material rich in 226Ra, assuming identical advection through the floor and that the wattle contains 50% soil and 50% lime and or sand, the activity of the wattle material used are 31 Bq kg  1, 110 Bq kg  1 and 155 Bq kg  1 for homes A, B and C respectively. Using the linear fit generated for block and steel homes, Fig. 2 and the same approximation previously established for the red mud house, and assuming that the advection rate is the same for all tiled concrete floors, yields radon activities that are shown in Table 2, Rn conventional. This approximation, Rn conventional, of radon content of the wattle daub home is based Table 1 Soil and home radon. HomeRn (Bq m  3) U (mg/g)

Parish of St. Elizabeth Contemporary House 1 89437 37.7 2 53420 32.9 3 26687 24.4 4 49625 24.4 Parish of St. Elizabeth Old House A 55080 79.2 B 93345 100 C 25174 24.4 Control House (Contemporary) C1 14756 3.6 C2 14519 10.2 C3 18314 3.9 Offices O1 19975 24 O2 19975 37

eU (mg/g)

12.0 2.8 5.7 10.8

36.8 17.4 6.13 15.8

11.8 10.7 5.9

18.1 25.8 7.6

1.8 1.6 2.2

1.1 1.0 2.6

2.8 2.8

3.3 3.3

4.2. Radon in the work place Radon concentration as a function of time was measured in an office and a laboratory at ICENS. Fig. 3a corresponds to measurements in a laboratory over a weekend. In this case there were a few peaks higher than 60 Bq m  3 with one maximum of 125 Bq m  3 with an average of 37 Bq m  3. A drastically drop in temperature, humidity and Radon is observed at the far end of curves in Fig. 3a, indicating the returning regular laboratory activities at the beginning of the week. These results are far below the lower limit of constraint set by the ICRP of 600 Bq m  3 for the work place.

Table 2 Estimation of advection contribution from unpaved soil beneath homes.

A B C

Measured Bq m  3

Calculated Bq m  3

Rn

Rnwattle

79.2 100 24.4

73.2 105 28.2

120

Rnconventional

Rnadvection

48.0 66.3 25.0

25.2 38.7 3.2

50

Temperature Humidity

80

The radon concentration in Green Grotto show cave, which is traversed regularly by tourist and tour guides, was rather constant and ranged from 30 Bq m  3 to 40 Bq m  3, temperature between 251C and 301C and humidity in the interval of 75–85%, Fig. 4a. The radon concentration in Xtabi open-ended sea cave at 10 Bq m  3 was very low and even below the detection limit of the

55

Radon

100

45 40

60

Time

14:24

9:36

4:48

0:00

25 19:12

0

14:24

30

9:36

20

4:48

35

0:00

40

19:12

Rn Bq/m3

& Daub

4.3. Radon in show caves

Temperature C Realtive Humidity %

Wattle and Daub Home

Detector Retuned to Laboratory

140

70

120 100

60 Radon

80

Temperature

60

Humidity

50 40

40

30

20

20

0 16:19

10 21:07

1:55 Time

Fig. 3. (a) Radon in laboratory, weekend, no air conditioning. (b) Radon in control house 3.

6:43

11:31

Temperature C Realtive Humidity %

SoilRn (Bq m  3) calculated

Rn Bq/m3

Sample

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C.N. Grant et al. / Applied Radiation and Isotopes 71 (2012) 96–101

3000

80 70

30 Average Rn Concentration ~28 Bqm-3 20

Radon Temperature Humidity

60 50 40

10

30

Radon concentration Bqm-3

Radon Concentration (Bqm-3)

40

Temperature °C, Relative Humidity (%)

90

Oxford Caves Manchester

90

Average Rn Concentration ~1859 Bqm-3

80

2500

70 2000 60 1500

50 Radon Temperature Humidity

1000

30

500

0 9:35 9:45 9:55 10:05 10:15 10:25 10:35 10:45 Time

40

14:00

14:20

14:40 15:00 Time

15:20

15:40

Temperature(°C) and Humidity(%)

100

20

Fig. 4. (a) Radon concentration in Green Grotto Cave. (b) Radon concentration in Oxford Cave.

Table 3 Places of study and constraint recommendation. Place

[Rn] Bq/m3

Constraint

Laboratory Control houses Houses high radioactive level in soil Green Gotto—Tourist Cave Xtabi—Tourist Cave Windsor—Speleologist and ecotourism cave Oxford—Speleologist Cave

60–125 20–35 24–38

Non Non Non

30–40 10 maximum 250–350

Non Non Non

2592

Yes: for less than 3 mSv/year, stay should not be more than 1.5 h/day or 400 h/year.

detector at times. This is most likely due to the wave action extracting air from the interior of the cave. The temperature and humidity were rather constant with values of 28 1C and 74% respectively. These results show that the tourist caves in this study presents no risk for the visiting tourist as the concentrations are far below the ICRP indoor limit of constraint 200 Bq m  3, and no risk to the tour guides and staff at these facilities, lower limit of constraint set by the ICRP of 600 Bq m  3 for the work place. 4.4. Radon in caves of speleological interest The Windsor cave which is frequently visited by speleologist and ecotourism had radon concentration in the range 250–350 Bq m  3, during the measurements temperature smoothly dropped from 32 1C to 25 1C as a heavy rain started and humidity increases from 64% to 78%. Based on the maximum measured radon concentrations this cave poses no threat to workers or tourist using this cave. The radon concentration in Oxford cave went up to 536 Bq m  3 in the first 10 min and reached a maximum of 2592 Bq m  3, temperature dropped from 29 1C to 24 1C as raining started outside the cave and rising the humidity from 65% to 86%. Based on the measured radon concentration and using the lower level of constraint of 3 mSv for work places it is recommended that potential tour guides for this cave spend no more than 1.5 h per day or 400 h per year, Fig. 4b, times exceeding this on a daily basis will result in doses greater than 3 mSv for the year. Table 3 presents the whole panorama of study places and constraint recommendations.

5. Conclusions The calculated soil gas radon, based on radium content of soil, and the measured house radon concentration are very well correlated for houses of similar construction. Based on island wide data collected on uranium and radium in Jamaican soils (Lalor and Miller, 1989) it is unlikely that homes of contemporary design will exceed the 200 Bq m  3 set by the ICRP as the lower limit of constraint for homes, partly because of the construction materials used and that tropical homes are typically well ventilated. Only homes constructed from local materials with wooden floorboards covering unpaved soil in areas of high soil radium (448 mg kg  1) will potentially exceed this level. Preliminary results indicate that a significant portion of the indoor radon this type of home can be attributed advection through the floor; primary intervention would therefore simply involve the concrete paving of the underlying soil. Fortunately, most of the elevated soil radium is located in remote areas of Jamaica with low population densities; to date, a soil radium content of 440 mg kg  1 have not thus far been reported for Jamaican soil and the practice of constructing homes solely from local materials is no longer performed. A more detailed study, targeting vulnerable (old) homes in the more in elevated areas highlighted in Fig. 1, will be needed before a comprehensive statement can be made on the radon risk for the entire population of the island. The concentration of radon in the measured office was similar to that of homes and is further reduced by use of air conditioning. Radon in modern offices is unlikely to reach lower limit of constraint set by the ICRP of 600 Bq m  3 for the work place based on a 2000 h per working year, as such, radon in the work place is not expected to pose a threat in Jamaica. The radon concentrations in caves vary significantly across Jamaica. A cursory review of the measured radon concentrations and the overlying soil radioactivity would suggest that they are related. The show caves, both of which are used regularly by tourist have very little radon present and pose no threat. It is the author’s belief that due to the geology of the island, other caves similarly located along coastline of Jamaica will also reflect these trends. Caves located in the interior of the island and in areas of high radioactivity will require a full survey to ascertain the levels of radon present. The two caves measured in the interior, both of which are of speleological and eco-tourist interest, exhibited elevated levels; the oxford caves in fact represent a hazardous work environment and time spent in this cave should be limited

C.N. Grant et al. / Applied Radiation and Isotopes 71 (2012) 96–101

101

Rn Concentration (Bqm-3)

Radon Exposure and Dose Constraints 100000 Rad.Worker UpperLimit

10000

LowerLimit 1000

100

10 20 mSv 1

10 mSv

Oxford Cave Time Limit (~2 hours per Day)

Standard working year

3 mSv

0.1 10

100

1000 10000 Hours per Year

100000

1000000

Fig. 5. Radon exposure and dose constraints in Oxford cave.

to less than 400 h per year (Fig. 5); this cave should therefore pose no threats to occasional eco-tourist. It is the authors recommendation that radon concentration and recommended hours of occupation per year of these caves be posted at the entrance, for serious speleologist, the unofficial tour guides and guano miners should consider making note of there estimated accumulated doses based on the posted information.

Acknowledgments To the ministries of foreign affairs of both countries, Jamaica and Mexico through a bilateral collaboration in the frame of the project ‘‘Geochemical Mapping of Soils and Food Crops in Selected Areas of Jamaica and Mexico Using Analytical Techniques’’, support this work. References Aley, T.J., 1964. Sea caves in the coastal karst of western Jamaica. Cave Notes 6, 1–3. Amiel, S., 1962. Analytical applications of delayed neutron emission in fissionable elements. Anal. Chem. 34, 1683–1687.

Ann. ICRP 23, 1993. ICRP Protection Against Radon-222 at Home and at Work. Publication 65. Balca´zar, M., 2008. Radiacio´n inducida y natural. Actividad Cientı´fica y Tecnolo´gica en el Instituto Nacional de Investigaciones Nucleares, Editorial Lagares pp. 428. Boulanger, A., Evans, D.J.R., Raby, B.F., 1975. Uranium analysis by neutron activation delayed neutron counting. Atomic Energy of Canada Ltd. Commercial Products report, 15. Duke, M.J.M., 1983. Geochemistry of the Exshaw Shale of Alberta. MSc Thesis. University of Alberta, Edmonton Alberta, Canada. Fincham, A., 1997. Jamaica Underground: The Caves, Sinkholes and Underground Rivers of the Island By, University of the West Indies Press, isbn:9766400369. Gates, A.E., Gunderson, C.S., 1992. Geologic controls on radon. Geol. Soc. Am. 10, 271–276. Grant, C.N., Lalor, G.C., Vutchekov, M.K., Balca´zar, M., 2001. Radon mapping of soils in St. Elizabeth Jamaica. J. Radioanal. Chem. 20, 295–302. Lalor, G.C., Miller, J.M., 1989. Gamma radiometric survey of Jamaica. Trans. Inst. Min. Metall. 98–104. Pinnock, W.R., 1999. Radon levels and related doses in a prototype Jamaican house constructed with bauxite waste blocks. Radiat. Prot. Dosim. 17, 291–299. Siemiatycki, J., Richardson, L., Straif, K., Latreille, B., Lakhani, R., Campbell, S., Rousseau, M.C., Boffetta, P., 2005. Environ. Health Perspect. 12, 113–117. United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), 1982. Report to the General Assembly. Ionizing radiation: Sources and Biological Effects, p. 157.