The hydroxyl (OH) radical is the most important oxidant in the atmosphere since it controls its self-oxidizing capacity. The main sources of OH radicals are the photolysis of ozone and the photolysis of nitrous acid (HONO). Due to the attenuation of solar radiation in the indoor environment, the possibility of OH formation through photolytic pathways indoors has been ignored up to now. In the indoor air, the ozonolysis of alkenes has been suggested as an alternative route of OH formation. Models and indirect measurements performed up to now according to this hypothesis suggest concentrations of OH radicals on the order of 10 4 –10 5 molecules per cubic centimeter. Here, we present direct measurements of significant amounts of OH radicals of up to 1.8⋅10 6 molecules per cubic centimeter during an experimental campaign carried out in a school classroom in Marseille. This concentration is on the same order of magnitude of outdoor OH levels in the urban scenario. We also show that photolysis of HONO is an important source of OH radicals indoors under certain conditions (i.e., direct solar irradiation inside the room). Additionally, the OH concentrations were found to follow a linear dependence with the product J(HONO)⋅[HONO]. This was also supported by using a simple quasiphotostationary state model on the OH radical budget. These findings force a change in our understanding of indoor air quality because the reactivity linked to OH would involve formation of secondary species through chemical reactions that are potentially more hazardous than the primary pollutants in the indoor air.

For self-measurement of blood pressure to be useful, patient reporting of test results must be reliable and accurate. Until now no study directly measured the accuracy and reliability of patients' reporting of self-measured blood pressure values. Thirty hypertensive patients (69 +/- 11 years) were instructed to measure blood pressure at home over 14 days with the highly accurate Omron IC monitor and to keep a record of all readings in a patient logbook. To assess the reliability of the records, patients were not informed about the memory capacity of the device. We compared automatically stored blood pressure readings with the respective logbook entries to analyze deletion (under-reporting), addition (over-reporting), and precision of reporting of test results. The prevalent pattern was under-reporting, averaging 36% +/- 24% (3% to 89%), which occurred significantly more than over-reporting (9% +/- 11%; 0% to 38%). The precision of reporting (identical values at corresponding times) was 76% +/- 34% (0% to 100%). This observer error did not affect group comparisons of automatically stored values and logbook entries, although the estimated limits of agreement were wide. Blood pressure control, duration of hypertension, age, or previous use of self-measurement and patterns of logbook entries were not found to be predictive of the patients' reliability. Our results demonstrate a substantial observer error in the reporting of self-measured blood pressure values. This bias may be reduced by memory-equipped blood pressure devices.

No abstract

No abstract