Rovira et al. claim formaldehyde is “a matter of health concern”, not only regarding nasal cancer and leukemia, but also non-carcinogenic effects are to be expected in Spain, on the basis of 8 hour air sampling in homes and workplaces. Measured concentrations are as expected, in general, in agreement with reported concentrations worldwide, e.g. (Salthammer et al., 2010), but substantially lower than in ambient air in major cities (Salthammer, 2013).

Thus, we wonder:

How concentrations are reported with such high precision of up to two significant digits after the comma, e.g. 3.37 µg/m3? It is our opinion that such precision is meaningless in view of the combined uncertainties of sampling and analysis. Furthermore, reporting such precision has no relevance whatsoever from a toxicological point of view.

Why the authors state that formaldehyde causes leukemia at indoor levels, despite several key publications clearly demonstrate the biological implausibility, e.g. (Golden, 2011;Nielsen et al., 2013;World Health Organization, 2010) and the unambiguous key experimental studies, e.g. (Kleinnijenhuis et al., 2013;Swenberg et al., 2013)? (See also statement by ECHA that classifies formaldehyde in Carc. 1B).

Why the authors apply unit risk calculations when there is a well-documented and established no effect level for cancer of 0.1 mg/m3 (World Health Organization, 2010) and furthermore  the concentration-response relationship is non-linear and biphasic?

Why the authors apply and cite grey literature, e.g. Kotzias et al. (2005) and Koistinen et al. (2008) (refs. 15 and 57, same work) when scientific progress has demonstrated the inadequacy of approach and the uncritical use of assessment factors for deriving guidelines; and, later overruled by the WHO (2010) documentation?

Why the long-term Canadian guideline is cited, well-knowing that it is based on a false presumption as discussed in detail by WHO (2010), Golden (2011) and Nielsen et al. (2013), and the US National Science Council (April 2011)?

Why the authors apply a RfD value for non-carcinogenic risk by OEHHA well-knowing that this value of 9 µg/m3 is based on one single inadequate study and the use of unjustified assessment factors, as discussed in detail in WHO (2010) and in (Golden, 2011;Nielsen et al., 2013;Wolkoff and Nielsen, 2010)?

Why the authors refer to “a chemical of concern, when levels exceed 1 µg/m3 (ref 57)”, well-knowing that humans exhale formaldehyde at a similar concentration and the guideline value was obtained by unjustified assessment factors, and later overruled by WHO (2010) and other key reviews?

 Reference List

Golden R (2011) Identifying an Indoor Air Exposure Limit for Formaldehyde Considering Both Irritation and Cancer Hazards. Critical Reviews in Toxicology 41:672-721.

Kleinnijenhuis AJ, Staal Y D E, Engel R and Woutersen R A (2013) The Determination of Exogenous Formaldehyde in Blood of Rats During and After Inhalation Exposure. Food Chem Toxicol 52:105-112.

Nielsen GD, Larsen S T and Wolkoff P (2013) Recent Trend in Risk Assessment of Formaldehyde Exposures From Indoor Air. Arch Toxicol 87:73-98.

Salthammer T (2013) Formaldehyde in the Ambient Atmosphere: From an Indoor Pollutant to an Outdoor Pollutant. Angew Chem Int Ed 52:3320-3327.

Salthammer T, Mentese S and Marutzky R (2010) Formaldehyde in the Indoor Environment. Chem Rev 110:2536-2572.

Swenberg JA, Moeller B C, Lu K, Rager J E, Fry R C and Starr T B (2013) Formaldehyde Carcinogenicity Research: 30 Years and Counting for Mode of Action, Epidemiology, and Cancer Risk Assessment. Toxicol Pathol 41:181-189.

Wolkoff P and Nielsen G D (2010) Non-Cancer Effects of Formaldehyde and Relevance for Setting an Indoor Air Guideline. Environ Int 36:788-799.

World Health Organization (2010) Selected Pollutants. WHO Indoor Air Quality Guidelines. WHO Regional Office for Europe, Copenhagen.