Homolytic pathways to aromatic bromo-compounds

The reactions of some polybromoanilines with pentyl nitrite in benzene at 80&deg; has been studied. 2,3,4,5,6-Pentabromobiphenyl was prepared by this method and also by the Ullmann reaction between iodobenzene, pentabromoiodobenzene, and copper powder. The yield of biaryl formed from homolytic arylation of benzene decreases as o-bromoaniline, 2,4,6-tribromoaniline or pentabromoaniline are the sources of the aryl radicals. This decrease is paralleled by an increase in the yield of the benzene derivative arising from the formal protodeamination of the parent aniline derivative. Evidence was also found of a heterolytic reaction accompanying the main homolytic arylation reaction which gives hexabromobenzene as a side-product in the reaction of pentabromoaniline and pentyl nitrite in benzene. Photochemical bromination reactions of some benzene derivatives, using molecular bromine as the source of bromine atoms, were performed. Both nuclear addition and nuclear substitution products were formed, the relative amounts of which vary with the benzene derivative since both polar and steric factors influence these reactions. However, it was found that the ratio of nuclear substitution to nuclear addition increased with increase in temperature from ca. 25 to ca. 50&deg;. Evidence (i.e. the photochemical decomposition of benzene hexabromide and of 1,2,3,4,5,6-hexabromochlorocyclohexane to give some di-halo-arenes) was adduced which suggests an addition-elimination mechanism as an interpretation of the formation of bromo-arenes in the photochemical bromination of benzene derivatives. Direct abstraction of hydrogen from a species such as C6H6Br&middot; seems unlikely by Br 2 on thermochemical grounds, but possible by Br&middot; or by a photochemically excited species Br2*. Partial rate factors for free radical bromination of biphenyl have been determined and discussed, although it is unlikely that they are capable of simple interpretation. The isomer distribution of bromo-arenes found here was quite different from the corresponding ratio reported for heterolytic reactions. The meta-positions of certain benzene derivatives, which are deactivated towards electrophiles in ionic reactions, were found to be readily attacked by bromine atoms.<p

Occupant health & well-being in green buildings: Trends and Future Directions

Expectations for high performance green buildings have been evolving over the last four decades. Green certification systems define, recognize, and demonstrate leadership in addressing building problems related to people and the environment. These systems are premised on a theory of change where making the distribution in building performance visible provides opportunities for competitive differentiation that motivates and rewards action to create better spaces, buildings, and places. To date, there are more than 200 different green building certification programs around the globe, with estimates of at least 1 million certified projects

Pilot study of sources and concentrations of size-resolved airborne particles in a neonatal intensive care unit

Infants in neonatal intensive care units (NICUs) are vulnerable to environmental stressors. Few studies have reported on airborne particles in the NICU environment. During a four-day pilot study in a private-style NICU, we measured size-resolved particle number (PN) concentrations with 1-min resolution. The investigation included simultaneous sampling in an unoccupied baby room and in an incubator of an otherwise normally functioning NICU. Background submicron (0.3-1 µm) particle levels in the room were 3-4 orders of magnitude lower than outdoors, owing to high-efficiency particulate filtration of supply air. Airborne supermicron particles were detected in the room; their presence was attributed primarily to emissions from occupant movements. The fraction of in-room PN detected within an infant incubator ranged from 0.2 for particles &gt;10 µm to 0.6 for particles with diameter 0.3-0.5 µm. The incubator humidifier was a strong additional source of particles smaller than 5 µm. Activities by researchers, designed to simulate caregiver visits, were associated with elevated particle concentrations across all measured size ranges, and were particularly discernible among larger particles. Concentrations increased with the number of occupants and with the duration and vigor of activities. The highest levels were observed when fabrics were handled. Against the low background in this environment, even small occupancy-associated perturbations – such as from a brief entry – were discernible. Measurements from a second NICU in a different US region were found to be broadly similar. A notable difference was higher submicron particle levels in the second NICU, attributed to elevated outdoor pollution

Inhalation intake fraction of particulate matter from localized indoor emissions

Elevated exposure to airborne particulate matter is linked to deleterious health and well-being outcomes. Exposure assessment can be improved through enhanced understanding of source-receptor relationships, for example as expressed in the inhalation intake fraction metric. This study provides new knowledge about how inhalation intake of airborne particles varies with spatially varying indoor emissions. In a controlled environmental chamber with low background particle levels, we monitored the time- and size-resolved particle concentrations at multiple locations including the subject's breathing zone. We investigated two types of particle emissions: (i) controlled releases from several specific indoor locations; and (ii) natural release from skin and clothing for a range of simulated occupant activities. Findings show that particles released proximate to the human envelope caused a total inhalation intake fraction of 7–10 per thousand, which was 1.5–16 × higher than the intake fraction for other indoor release locations. These outcomes reflect the influence of emissions-receptor proximity combined with the efficient transport of particles by means of the thermal plume to the breathing zone. The results show that the well-mixed representation of an indoor environment could underestimate the inhalation intake by 40–90% for various localized indoor emissions, and by up to 3 × for particles emitted from the human envelope. The post-release exposure period contributed substantially to total inhalation intake. For particles released naturally from the human envelope, inhalation intake fractions varied with activity type and were higher for a subject when seated rather than walking