Correspondence/Rebuttal pubs.acs.org/est
Comment on “High Naturally Occurring Radioactivity in Fossil Groundwater from the Middle East”
V
engosh et al.1 conducted a study on the Disi aquifer in Jordan in order to understand how salinity is correlated with radioactivity, to evaluate the sources of radium in the groundwater and to investigate the possible mechanisms of radium mobilization. The activity concentration of three αemitting isotopes, namely 226,224,223Ra, in addition to the βemitting 228Ra, were measured in thirty-seven groundwater samples. The study covered the Rum-group aquifer, the Khreim-group in Disi-Mudawwara and areas in Central Jordan. That study ultimately revealed the Disi water to be highly radioactive, thus surrounding the Disi conveyance project with controversy. The paper reported the combined 226Ra and 228Ra activities to be much higher than international drinking-water standards. The reported data raised concerns over the safety of Disi and similar nonrenewable groundwater reservoirs, intensifying the already severe water crisis in the region. That important paper was cited not only in different reports (e.g., refs 2−4), but also repeatedly in local and international media, hence became the focus of attention for a continued debate over the indispensable Disi conveyance project. Jordan has already one of the lowest levels of water resource availability per capita in the World. Management of water resources is therefore a key issue facing national government authorities.5,6 In July 2013, Jordan began pumping water from the southern fossil aquifer of Disi, a $990 million project which involves digging 55 wells and piping water supplies 325 km to the capital city Amman, as well as to other governorates. The lifespan of this nonrenewable water conveyance project is estimated at 20−30 years if abstraction rates are kept at around 100 million cubic meters (mcm) each year. The project hence provides a provisional solution to a long-term problem, but provides Jordan with enough time to consider other options like desalination.5 Therefore, the Disi resource is of vital importance to the country, especially amid the unrest in the region which imposes direct multifold impact on Jordan, one of which is related to hosting significant numbers of refugees. The hydrogeological nature of that study did not require the calculation of the corresponding effective dose delivered to consumers. Therefore, Table 1 of the Vengosh et al. paper only lists the measured activity concentration (in Bq/l) for the four radium isotopes. Though the table compares these activity concentration values to the corresponding international requirements and guidelines on activity, but no dose calculation and comparison with international standards was implied at that stage by the objectives of the Vengosh study. The current comment aims at a further analysis of the same raw data reported in Table 1 of the Vengosh et al. paper. In addition to radioactivity concentration, this work evaluates the committed effective annual dose from the radium isotopes. The dose is calculated from the individual radionuclide concentration assuming annual consumption of 730 L.7 The radiotoxicity of a nuclide is determined by its effective dose coefficient, which accounts for radiation and tissue weighting factors and metabolic information. The coefficients are © 2014 American Chemical Society
obtained from the International Commission on Radiological Protection ICRP 2012 report.8 Private communication with the Water Authority of Jordan WAJ indicated that water currently pumped from the wells arrive at the reservoirs after a minimum period of 2.7 days. Though this period does not include an additional time to reach households through the distribution network, the 2.7 days period was adopted for a conservative estimate of the decay of the relatively short-lived radium isotopes, namely 223Ra and 224Ra, with half-life times T 1/2 of 11.435 and 3.66 days,9 respectively. The activity concentration screening levels of 0.5 Bq/L for gross-alpha and 1 Bq/L for gross-beta, as set by the WHO,7 are obviously exceeded. Since consumption of radium in drinkingwater increases risks for bone cancer and leukemia, it was noted that many Rum-group wells exceed the derived concentration of 0.5 Bq/L (or 1 Bq/L) for 226Ra and most Rum-group wells exceed the derived concentration of 0.2 Bq/L (or 0.1 Bq/L) for 228 Ra, as set by the European Union10 (or in the WHO guidelines7). The combined 226Ra and 228Ra activities also exceed the U.S. EPA limit of 5 pCi/L.11 Consequently, the committed effective annual dose from individual radionuclides are considered (Figure 1). Obviously, the annual dose from the
Figure 1. Dose contribution of the four radium isotopes for individual wells in each of the Disi aquifer groups. A conservative delay period of 2.7 days for water pumped from each well to reach the collection/ mixing reservoir has been assumed.
Rum-Group as well as from Central Jordan wells is high compared to the 0.1 mSv/a recommended in the WHO Guidelines.7 It is worth mentioning that in October 2013, the European Union adopted the same WHO guideline value of 0.1 mSv/a.10 Nevertheless, the very same WHO report emphasizes the fact that “It is essential that each country review its needs and capacities in developing its regulatory framework”. It also mentions that no international standards for drinking-water quality are promoted for adoption. In particular, the report Published: July 31, 2014 9943
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Correspondence/Rebuttal
Jordanian standards for part of the population, while the other part continues using lower-activity non-Disi water, mixing aims at achieving compliance with the Jordanian standard for all consumers in the country. The results reveal the radiological quality of the indispensable Disi drinking-water to be satisfactory for consumption in a water-poor part of the World, if risks are carefully managed. The author is preparing an extended manuscript that includes a risk-benefit analysis. Blending ratios should take into consideration any possible buildup of the nonmobile 228Th in the system, which could affect the 224Ra concentration. Continuous and routine monitoring, including sample collection and measurement, is essential to ensure compliance with the local standards. Transparency in the governmental water policies psychologically enhances the public acceptance. Practically, decision on blending ratios should always take into consideration the importance to reduce risk as much as reasonably achievable. However, the availability and quality of surface water, to a given reservoir, could be a limiting factor. Water treatment facilities should be considered locally in regions with limited availability of surface water resources. Proposals for water desalination in the Gulf of Aqaba, which is intended to provide a more sustainable supply, can be also considered as a future resource for blending which can take place on-site in the south, eliminating the necessity for regional blending. This scenario enables freeing surface water resources to be available to other usage.
emphasizes that exceeding a guidance level should be taken as a trigger for further investigation, but not necessarily as an indication that the drinking-water is unsafe. The abovementioned guidelines on activity concentration of 1 Bq/L and 0.1 Bq/L for 226Ra and 228Ra, respectively, are derived from the recommended dose of 0.1 mSv/a. In this context, the 2011 Australian Drinking-Water Guidelines12 recommends a guideline dose of 1 mSv per year to be applied. This is ten times the corresponding WHO value. The Australian document does not consider its recommended dose as a mandatory limit, but when exceeded, a decision on the need for remedial action should be based on a cost−benefit analysis, and there may be circumstances where there is no practical alternative but to accept a dose that exceeds this guideline. The Australian guideline value is based on earlier studies.13,14 In Jordan, however, a mandatory regulation sets a maximum dose of 0.5 mSv/a,15 which if exceeded, a limited time period is allowed to consider operational options to secure compliance. Therefore, in addition to the WHO guideline, both Australian guideline and Jordanian standard values are indicated in Figures 1 and 2. The average dose from each group is
Saed Dababneh*
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Department of Physics, Faculty of Science, Al-Balqa Applied University, P.O. Box 2587, Amman 11941, Jordan
AUTHOR INFORMATION
Corresponding Author
*Phone: +962-7-95606613; fax: +962-6-5341608; e-mail:
[email protected]. Notes
The authors declare no competing financial interest.
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Figure 2. Average radium dose according to three mixing models with non-Disi water with a conservative 0.15 mSv annual dose.16
REFERENCES
(1) Vengosh, A.; Hirschfeld, D.; Vinson, D.; Dwyer, G.; Raanan, H.; Rimawi, O.; Al-Zoubi, A.; Akkawi, E.; Marie, A.; Haquin, G.; Zaarur, S.; Ganor, J. High naturally occurring radioactivity in fossil groundwater from the Middle East. Environ. Sci. Technol. 2009, 43, 1769−1775. (2) Upson, S. Jordans radioactive water problem. Spectrum IEEE 2009, 46, 13−15. (3) Bonotto, D. M. Natural radionuclides in major aquifer systems of the Paraná sedimentary basin, Brazil. Appl. Radiat. Isot. 2011, 69, 1572−1584. (4) Szabo, Z.; dePaul, V. T.; Fischer, J. M.; Kraemer, T. F.; Jacobsen, E. Occurrence and geochemistry of radium in water from principal drinking-water aquifer systems of the United States. Appl. Geochem. 2012, 27, 729−752. (5) Jaber, J. O.; Mohsen, M. S. Evaluation of non-conventional water resources supply in Jordan. Desalination 2001, 136, 83−92. (6) World Health Organization. HELI Technical Advisory Group in Jordan. http://www.who.int/heli/pilots/jordan/en/ (accessed September 2013). (7) Guidelines for Drinking-Water Quality, 4th ed.; World Health Organization, 2011. (8) Compendium of Dose Coefficients Based on ICRP Publication 60, ICRP Publication 119. Ann. ICRP 41 (Suppl.); The International Commission on Radiological Protection, 2012.
depicted in the white column (solid border) of Figure 2. Water from the Khreim-group could comply with the conservative WHO recommendation, while the average dose from Central Jordan wells could satisfy the Jordanian standard. The unconfined and confined Rum-group slightly exceed the Jordanian dose limit and the Australian guideline, respectively. Needless to say, water treatment could considerably reduce radium concentration and hence the associated dose to levels well below the Jordanian standard. This was also recommended by Vengosh et al. An alternative cost-effective solution could potentially be considered, that is, to develop a crude model for blending groundwater with, for exmaple, surface water in a local reservoir. This is intended to provide a qualitative assessment about the effectiveness of such mixing on reducing the dose to consumers. To make this model as conservative as possible, a dose of 0.15 mSv/a is adopted for the non-Disi resource,16 which is already higher than the WHO recommendation. Mixing ratios of Disi:Non-Disi = 1:1, 2:1 and 1:2 are considered and depicted in Figure 2. According to such very conservative models, a dose of less than the WHO guideline is definitely not achievable. Nevertheless, and instead of exceeding 9944
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(9) Chu, S.; Ekström, L.; Firestone, R. WWW Table of Radioactive Isotopes, The Lund/LBNL Nuclear Data Search, Version 2.0, 1999. http://nucleardata.nuclear.lu.se/toi/index.asp (accessed September 2013). (10) COUNCIL DIRECTIVE 2013. Laying down requirements for the protection of the health of the general public with regard to radioactive substances in water intended for human consumption. http://register.consilium.europa.eu/pdf/en/13/st07/st07445-re03. en13.pd. (11) US-EPA Drinking water: Radionuclides Rule. http://water.epa. gov/lawsregs/rulesregs/sdwa/radionuclides/compliancehe. (12) Australian Drinking Water Guidelines 6; Australian Natural Resource Management Ministerial Council, National Health and Medical Research Council: Canberra, Australia, 2011; Vol. 1. (13) Recommendations for Limiting Exposure to Ionising Radiation, Radiation Health Series No. 39, Government Publishing Service, Canberra; NHMRC National Health and Medical Research Council: Canberra, Australia, 1995. (14) Lokan, K. Drinking water quality in areas dependent on groundwater. Radiation Protection in Australasia 1998, 15, 11−14. (15) Technical Regulation (Mandatory) 286/2008 on Water - Drnking Water (in Arabic); Jordan Standards and Metrology Organization: Amman, Jordan, 2008. (16) Al-Amir, S. M.; Al-Hamarneh, I. F.; Al-Abed, T.; Awadallah, M. Natural radioactivity in tap water and associated age-dependent dose and lifetime risk assessment in Amman, Jordan. Appl. Radiat. Isot. 2012, 70, 692−698.
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