Hostname: page-component-cd9895bd7-p9bg8 Total loading time: 0 Render date: 2024-12-25T07:41:58.236Z Has data issue: false hasContentIssue false

Limit of detection values in data analysis: Do they matter?

Published online by Cambridge University Press:  09 January 2012

M.D. Wood
Affiliation:
School of Science & the Environment, Manchester Metropolitan University, Manchester, M1 5GD, UK
N.A. Beresford
Affiliation:
Centre for Ecology & Hydrology, Bailrigg, Lancaster, LA1 4AP, UK
D. Copplestone
Affiliation:
School of Biological & Environmental Sciences, University of Stirling, Stirling, FK9 4LA, UK
Get access

Abstract

Data sets containing values below the limit of detection (LOD) are known as ‘censored data sets’. Such data sets are encountered regularly in most fields of environmental contaminant research. The current norm within environmental radioactivity research is to use substitution methods when analysing data sets that include values below the LOD, commonly replacing each LOD value with a value equal to half the LOD (LOD/2). However, this approach has no statistical basis and has implications when summarising or comparing data sets because it can lead to underestimates or overestimates of both the mean and the standard deviation. To remove the need to apply substitution methods, over the last four decades other fields of environmental science have been adopting statistical techniques developed for medical research applications. Despite the long history of applying these techniques in other fields and two recent environmental radioactivity publications that have used survival analysis techniques, there still seems to be reluctance within the environmental radioactivity research community to adopt these ‘new’ methods. This paper introduces the statistical techniques that can be used in place of LOD substitution, presents some guidance on the applicability of these techniques for different levels of data censoring and provides some examples of the use of these methods in various contexts. It is hoped the present paper will contribute to the evidence-base supporting the use of survival analysis within the field of environmental radioactivity research and go some way to changing the current norm of substitution using LOD/2.

Type
Research Article
Copyright
© Owned by the authors, published by EDP Sciences, 2011

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

EC, Commission Recommendation of 18 December 2003 on standardised information on radioactive airborne and liquid discharges into the environment from nuclear power reactors and reprocessing plants in normal operation. Official Journal of the European Union(2004).
Helsel, D.R., Nondetects and data analysis: statistics for censored environmental data. (John Wiley & Sons Inc., New Jersey, 2005)
Helsel, D.R., Environ Sci Technol 24 (1990) 1766-1774.
Baccarelli, A., Pfeiffer, R., Consonni, D., Pesatori, A.C., Bonzini, M., Patterson, D.G., Bertazzi, P.A., Landi, M.T. Chemosphere 60 (2005) 898-906.
Gleit, A., Environ Sci Technol 19 (1985) 1201-1206.
Brown, J.E., Alfonso, B., Avila, R., Beresford, N.A., Copplestone, D., Prohl, G., Ulanovsky, A., J Environ Radioact 99 (2008) 1371-1383.
Helsel, D.R., Chemosphere 65 (2006) 2434-2439.
Fievet, B., Della Vedova, C., J Environ Radioact 101 (2010) 1–7.
Wood, M.D., Beresford, N.A., Semenov, D.V., Yankovich, T.L., Copplestone, D., Radiat Environ Biophys 49 (2010) 509-530.
Garcia-Fernandez, A.J., Gomez-Ramirez, P., Martinez-Lopez, E., Hernandez-Garcia, A., Maria-Mojica, P., Romero, D., Jimenez, P., Castillo, J.J., Bellido, J.J., Ecotoxicol Environ Saf 72 (2009) 557-563.
Tajimi, M., Uehara, R., Watanabe, M., Oki, I., Ojima, T., Nakamura, Y., Chemosphere 61 (2005) 1256-1262.
Vitaliano, J.J., Zdanowicz, V.S., Marine Pollut Bull 24 (1992) 364-367.
Beresford, N.A., Barnett, C.L., Howard, B.J., Scott, W.A., Brown, J.E., Copplestone, D., J Environ Radioact 99 (2008) 1393-1407.
Hosseini, A., Thorring, H., Brown, J.E., Saxen, R., Ilus, E., J Environ Radioact 99 (2008) 1408-1429.
IAEA (International Atomic Energy Agency), Handbook of parameter values for the prediction of radionuclide transfer in Wildlife (IAEA, Vienna, 2011) (Draft in press)
US EPA, Guidance for data quality assessment. Practical methods for data analysis. (Office of Environmental Information, Washington DC, 2000).
Geras’kin, S., Oudalova, A., Michalik, B., Dikareva, N., Dikarev, V., Chemosphere 83 (2011) 1133-1146.
Antweiler, R.C., Taylor, H.E., Environ Sci Technol 42 (2008) 3732-3738
Glass, D.C., Gray, C.N., Ann Occup Hyg 45 (2001) 275–282.
Hornung, R.W., Reed, L.D. Appl Occup Environ Hyg 5 (1990) 46-51.
She, N., J Am Water Resour Assoc 33 (1997) 615-624.
Zhang, D.H., Fan, C.P., Zhang, J., Zhang, C.H., Stat Med 28 (2009) 700-715.
Kaplan, E.L., Meier, P., J Am Stat Assoc 53 (1958) 457-481
Brady, D., Pratt, G.C., J Air Waste Manag Assoc 57 (2007) 1091-1102.
Leese, M. N., Water Resour Res 9 (1973) 1534-1542.
Millard, S.P., Deverel, S.J., Water Resour Res 24 (1988) 2087-2098.
Leith, K.F., Bowen, W.W., Wierda, M.R., Best, D.A., Grubb, T.G., Sikarske, J.G., Chemosphere 80 (2010) 7–12.