Regulations on e-cigarettes in the U.S. do not provide guidelines on the chemical content of e-cigarette liquids. We evaluated emissions of aldehydes and flavoring chemicals in e-cigarette vapor under typical usage conditions. We selected 24 e-cigarette flavors from the top selling disposable e-cigarette brands. E-cigarettes were connected to a pump drawing air for two second puffs with sixty-second intervals between puffs. The vapor was analyzed for the presence of aldehydes using high-performance liquid chromatography-ultraviolet detector and for the presence of flavoring chemicals with gas chromatography and an electron capture detector. All e-cigarette emissions tested contained at least one aldehyde and/or flavoring chemical on either the FEMA "High Priority Chemicals" or FDA Harmful and Potentially Harmful Constituents lists when sampled at typical usage conditions. Diacetyl, a known respiratory hazard, along with acetoin, were the most prevalent of the flavoring chemicals in e-cigarette vapor, being found in more than 60% of samples. The presence of propionaldehyde, acetaldehyde and formaldehyde were correlated, corroborating previous work suggesting thermal degradation as a pathway for aldehyde generation in e-cigarette vapors. Median formaldehyde concentrations of 626 μg/m in e-cigarette vapor exceed the ACGIH maximum concentrations allowable for workers of 370 μg/m.

Animals communicating via scent often deposit composite signals that incorporate odorants from multiple sources; however, the function of mixing chemical signals remains understudied. We tested both a ‘multiple-messages’ and a ‘fixative’ hypothesis of composite olfactory signalling, which, respectively, posit that mixing scents functions to increase information content or prolong signal longevity. Our subjects—adult, male ring-tailed lemurs (Lemur catta)—have a complex scent-marking repertoire, involving volatile antebrachial (A) secretions, deposited pure or after being mixed with a squalene-rich paste exuded from brachial (B) glands. Using behavioural bioassays, we examined recipient responses to odorants collected from conspecific strangers. We concurrently presented pure A, pure B and mixed A + B secretions, in fresh or decayed conditions. Lemurs preferentially responded to mixed over pure secretions, their interest increasing and shifting over time, from sniffing and countermarking fresh mixtures, to licking and countermarking decayed mixtures. Substituting synthetic squalene (S)—a well-known fixative—for B secretions did not replicate prior results: B secretions, which contain additional chemicals that probably encode salient information, were preferred over pure S. Whereas support for the ‘multiple-messages’ hypothesis underscores the unique contribution from each of an animal's various secretions, support for the ‘fixative’ hypothesis highlights the synergistic benefits of composite signals.

An increased breast cancer risk during adulthood has been linked to estrogen exposure during fetal life. However, the impossibility of removing estrogens from the feto-maternal unit has hindered the testing of estrogen’s direct effect on mammary gland organogenesis. To overcome this limitation, we developed an ex vivo culture method of the mammary gland where the direct action of estrogens can be tested during embryonic days (E)14 to 19. Mouse mammary buds dissected at E14 and cultured for 5 days showed that estrogens directly altered fetal mammary gland development. Exposure to 0.1 pM, 10 pM, and 1 nM 17 β-estradiol (E2) resulted in monotonic inhibition of mammary buds ductal growth. In contrast, Bisphenol-A (BPA) elicited a non-monotonic response. At environmentally relevant doses (1 nM), BPA significantly increased ductal growth, as previously observed in vivo, while 1 μM BPA significantly inhibited ductal growth. Ductal branching followed the same pattern. This effect of BPA was blocked by Fulvestrant, a full estrogen antagonist, while the effect of estradiol was not. This method may be used to study the hormonal regulation of mammary gland development, and to test newly synthesized chemicals that are released into the environment without proper assessment of their hormonal action on critical targets like the mammary gland.

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