Letter to the Editor
Response to Risotto et al
Article first published online: 9 JAN 2013
© 2012 John Wiley & Sons A/S. Published by Blackwell Publishing Ltd
Volume 23, Issue 1, pages 87–88, February 2013
How to Cite
Bornehag, C.-. G., Carlstedt, F. and Jönsson, B. A. (2013), Response to Risotto et al. Indoor Air, 23: 87–88. doi: 10.1111/ina.12011
- Issue published online: 9 JAN 2013
- Article first published online: 9 JAN 2013
- Accepted manuscript online: 5 NOV 2012 02:03AM EST
Our article in this issue of Indoor Air on PVC flooring and its association with urinary levels of butyl benzyl phthalate (BBzP), metabolites in infants—criticized by Risotto et al.,—is part of a number of studies in which we focused on PVC and potential endocrine-disrupting chemicals, such as phthalates, in relation to human health. Results from our studies as well as those from other research groups have shown that the presence of vinyl flooring and phthalates in indoor dust is associated with both human biomarkers of phthalates and respiratory diseases and eczema in children (Bornehag and Nanberg, 2010). The presence of PVC in flooring materials has been associated with asthma, wheezing, and/or eczema in at least seven different epidemiological studies globally (as described in Bornehag and Nanberg, 2010). While some of the initial studies were cross-sectional, they are consistent with more recent longitudinal data. We reported that PVC flooring material in the home during infancy was significantly associated with the incidence of asthma in children five years later (Larsson et al., 2010). Further studies have shown that phthalates in indoor dust were associated with asthma and eczema in children in Sweden (Bornehag et al., 2004) and in Taiwan (Hsu et al., 2012) with the strongest association for BBzP. In Bulgarian data, an association was shown between diethylhexylphthalate (DEHP) in indoor dust and wheezing in children (Kolarik et al., 2008). There is further recent data from a New York city cohort showing that prenatal exposure of BBzP metabolites in pregnant women was associated with eczema in offspring (Just et al., 2012a), and BBzP metabolites in children was, in cross-sectional analyses, associated with exhaled nitric oxide, a biomarker of airway inflammation (Just et al., 2012b). Together, these studies support our statement that PVC in the indoor environment may include DEHP and BBzP and serves as a source for human uptake of BBZP and perhaps other phthalates.
To respond to the criticisms raised from Risotto et al., point by point, we offer the following remarks:
- Risotto et al., express concern that data on the type of flooring in homes were from parental reports rather than professional evaluation of the flooring type. While it is correct that data in this study are from questionnaire reports, we previously validated this item by comparing parental reports with the observations of a professional inspector (Hagerhed-Engman et al., 2007). We found that the extent of agreement between parental and professional reports on flooring type was lower for PVC and linoleum than for wood and laminate. Therefore, there was likely some misclassification of flooring type in this study. However, subjects did not know their measured phthalate levels, so any misclassification could only dilute the associations we found between PVC flooring and urinary levels of BBzP metabolites.
- Risotto et al., state that we have not proved that PVC floorings in the home included phthalates and that in Europe, as a result of REACH legislation, phthalates have been replaced by other plasticizers in PVC flooring materials. It is correct that we have not analyzed the content of phthalates in the studied flooring materials, and it is reasonable to assume that phthalates, such as DEHP, are used less frequently today in new PVC flooring materials in Europe, having been replaced in many cases by di-isononyl phthalate (DINP). But it should be pointed out that PVC flooring materials can be up to 20 years old before they are replaced. This means that a great part of the used PVC materials in this study most probably includes both DEHP and BBzP. Furthermore, we have shown in an earlier study that the use of PVC flooring in homes was significantly related to both DEHP and BBzP levels in indoor dust (Bornehag et al., 2005). It is therefore reasonable that our data are valid and that one source for BBzP metabolites in infant's urine is from the PVC flooring materials in the homes we studied.
- Risotto et al., further state that there is a need for data on dust concentrations of the selected phthalates to obtain conclusive data. We agree that this study would have been improved with data on dust levels of phthalates. However—and as described earlier—we have shown previously that PVC flooring is related to DEHP and more significantly to BBzP levels in indoor dust (Bornehag et al., 2005), indicating that the PVC material is a source. We also agree that Becker et al. (2004) did not find an association between the dust concentrations of DEHP and DEHP metabolites in children. But the results from Becker et al. (2004) are in line with our current results as we did not find any association between PVC and DEHP metabolites in the infants, but rather an association was observed between PVC and BBzP metabolites. In addition, there are several other studies indicating that BBzP levels in dust and air can be related to human urinary levels. In German data (Kolossa-Gehring et al., 2011) and in Taiwanese data (Hsu et al., 2012), BBzP in dust was significantly related to urinary levels of MBzP in children, but no such relationship was observed for DEHP. Data from a New York cohort have, in two studies, shown that the levels of BBzP in indoor air were related to urinary levels of MBzP in pregnant women (Adibi et al., 2003, 2008), but no such relationship was found for DEHP. We agree with Risotto et al., that it would have been better to have dust concentrations of phthalates in the current study, but the lack of such data does not make our study inconclusive. And as shown earlier, our findings are in line with results from other studies.
- Risotto et al., finally express concerns about the way we collected the urine from the children. The urine was collected by the use of phthalate-free polyethylene and phthalate-free sanitary towels and sampled in laboratory urine tubes. But we agree that there can be risks for contamination due to the way we collected and stored the urine. However, we cannot see why such a bias should drive our statistical analyses to an association between PVC flooring and MBzP urinary levels in infants; rather, the opposite should be expected. A contamination should also most probably be a diester (DEHP and BBzP) with rather limited impact on the monoester that we measured in the urine. Furthermore, the BBzP metabolite levels we are reporting in the criticized paper are well in concordance with the levels reported in seven other studies from Europe, USA, and South-East Asia, reported in the last table of the article. Consequently, we do not agree that the way we sampled the urine should be a reason for not believing in our results.
We therefore believe that our findings are valid and that they should be considered when designing indoor environments in homes, day care centers, schools, and offices.
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