Investigation of number of replicate measurements required to meet cigarette smoke chemistry regulatory requirements measured under Canadian intense smoking conditions.

There has been increased interest in recent years in regulatory reporting of cigarette smoke toxicants. There is a great deal of diversity in current regulatory standards around the world in terms of the identities of regulated toxicants, and the number of replicate analyses stipulated for their measurement. Furthermore, analytical methods developed collaboratively by several organisations and intended for regulatory analysis generally differ in their recommended replicate numbers to those stipulated by regulators.

Impact assessment of WHO TobReg proposals for mandated lowering of selected mainstream cigarette smoke toxicants.

The WHO Tobacco Product Regulation Study Group (TobReg) has proposed three regulatory models for cigarettes, each creating mandatory limits for emissions of nine smoke toxicants. One approach proposes country-specific limits, using median or 1.25× median toxicant/nicotine emission ratios.

Detecting long-term metabolic shifts using isotopomers: CO2-driven suppression of photorespiration in C3 plants over the 20th century.

Terrestrial vegetation currently absorbs approximately a third of anthropogenic CO2 emissions, mitigating the rise of atmospheric CO2. However, terrestrial net primary production is highly sensitive to atmospheric CO2 levels and associated climatic changes. In C3 plants, which dominate terrestrial vegetation, net photosynthesis depends on the ratio between photorespiration and gross photosynthesis.

Elucidating turnover pathways of bioactive small molecules by isotopomer analysis: the persistent organic pollutant DDT.

The persistent organic pollutant DDT (1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane) is still indispensable in the fight against malaria, although DDT and related compounds pose toxicological hazards. Technical DDT contains the dichloro congener DDD (1-chloro-4-[2,2-dichloro-1-(4-chlorophenyl)ethyl]benzene) as by-product, but DDD is also formed by reductive degradation of DDT in the environment. To differentiate between DDD formation pathways, we applied deuterium NMR spectroscopy to measure intramolecular deuterium distributions (2H isotopomer abundances) of DDT and DDD.

Baseline isotopic data of polyhalogenated compounds.

The delta2H- and delta13C-values of polyhalogenated compounds were determined by EA-IRMS. Most of the compounds were related to the chloropesticides DDT and its metabolites, hexachlorocyclohexanes, and toxaphene, as well as several polybrominated compounds such as bromophenols and -anisoles. delta2H-values ranged between -235 per thousand and +75 per thousand whereas delta13C-values were found in the range -22 per thousand to -38 per thousand.

Quantification of deuterium isotopomers of tree-ring cellulose using nuclear magnetic resonance.

Stable isotopes in tree rings are important tools for reconstruction of past climate. Deuterium (D) is of particular interest since it may contain climate signals and report on tree physiology. Measurements of the D/H ratio of tree-ring cellulose have proven difficult to interpret, presumably because the D/H ratio of the whole molecule blends the abundances of the seven D isotopomers of cellulose.

Hydrogen exchange during cellulose synthesis distinguishes climatic and biochemical isotope fractionations in tree rings.

The abundance of the hydrogen isotope deuterium (D) in tree rings is an attractive record of climate; however, use of this record has proved difficult so far, presumably because climatic and physiological influences on D abundance are difficult to distinguish. Using D labelling, we created a D gradient in trees. Leaf soluble sugars of relatively low D abundance entered cellulose synthesis in stems containing strongly D-labelled water.