With reference to your interview with the new head of the ACC, Cal Dooley (Chemistry World , September 2008, p9), bisphenol A (BPA) and phthalates are just two of several hundred chemicals that exhibit oestrogenic activity (EA) in plastics. These chemicals leach from almost all plastics sold today, including polyethylene, polypropylene, polyethylene terephthalate (PET), etc. That is, plastics advertised as BPA-free or phthalate-free are not EA-free; almost all these plastics still leach chemicals having EA - and often have more total EA than plastics that release BPA or phthalates.
Current legislation is attempting to solve this problem by removing chemicals having EA (BPA, phthalates) one at a time. This approach, for legislators or the FDA, is not an appropriate solution for consumers because thousands of chemicals used in plastics exhibit EA, not just BPA and phthalates. This approach is a marketing-driven solution, not a health-driven solution. The appropriate health-driven solution is to manufacture safer plastics that are EA-free. This is not a pie-in-the-sky solution, as the technology already exists to produce EA-free plastics that have the same advantageous physical properties as almost all existing EA-releasing plastics on the market today. In fact, some of these advanced-technology EA-free plastics are already in the marketplace. The cost of these safer EA-free plastics are just pennies more than EA-releasing plastics, when both are used to manufacture the same product in similar quantities.
G Bittner,
Texas, US
I enjoyed the articles on water in the September issue, probably because in the 1980’s I was the chemist in a small private company involved with the potable water and ’preowned food’ (sewage) industry in Europe.
In particular, the constantly improving analytical techniques for finding vanishingly small quantities of potentially harmful chemicals brought to mind several instances when I understood finally the true meaning of ’ignorance is bliss’.
My experiences were almost always the same, as soon as the regulatory authorities were made aware of the possible problem with a newly discovered contaminant a new regulation would appear. My problem, then and now, was that I understood and agreed that if I were in their position, I probably would have done the same.
At my age of 72, my experiences suggest that information overload is an escalating problem for regulatory authorities and the only solution I see will be when everyone accepts that the cost of doing something is not worth the extra longevity claimed for the solutions.
Just before I retired in 2004, I was working in the US and had to deal with the California proposition 65, where the proposed limits on crystalline silica were well below detection limits and would have meant the local authorities could have closed the beaches! Definitely time to retire.
W Anderson CChem MRSC,
by email
It is understandably rare for authors to respond in print to an independent review but we feel compelled to respond to the review by Stephen Jenkins of our book (Chemistry World, August 2008, p72). Although it was considered to be ’excellent’ the reviewer had strong reservations regarding ’the role of highly-reactive transient species described as both vibrationally and electronically "hot" for life-times in the order of picoseconds’. The review further states that we ’refer repeatedly to transient oxygen species as electronically non-thermal’. We did not use these specific descriptions in our model; rather our model is that of a metastable oxygen transient with translational kinetic energy. We make the following observations and comments.
Concepts in science usually evolve with time and persistent enquiry rather than as a result of a single experiment, even though that experiment may have been the spark that initiated the train of thought that led to more detailed examinations of the concept. In a paper in Nature in 1986, followed by a more detailed one in J. Chem. Soc. Faraday Trans. we discussed the possible limitations of classical mechanisms to describe surface oxidation reactions. Central to our argument were novel coadsorption studies which, using ammonia as a probe molecule, provided evidence for the role of ’hot’ oxygen adatom transients in the dynamics of the dissociative chemisorption of O2, NO and N2 O at metal surfaces. They also provided a different view of the catalytic oxidation of NH3 and subsequently were shown to be applicable to a wide range of reactions (Table 2.1) with metastable oxygen transients with translational kinetic energy undergoing surface diffusion being the active sites. There is a full discussion in Chapters 1 and 2 as to how the model illustrated in Figure 2.5 was developed and the limitations of the more traditional static approach in understanding reactivity.
The availability of Scanning Tunnelling Microscopy (STM) allowed the model based on surface spectroscopies (XPS and HREELS) to be examined at the atom-resolved level and support came in 1992 from Ertl’s group who showed that following the dissociative chemisorption of oxygen at Al (111) at 300K the two oxygen adatoms did not occupy adjacent surface sites - the classical picture - but were separated by 80? (see ref 7, Chapter 4, Brune et al, Phys Rev Lett, 1992, 68, 624). Part of the chemisorption energy had been transformed into translational kinetic energy and which Ertl (as we had) described as "hot" adatoms with a surface life-time of ? 1ps with each estimated to have an initial velocity of 6.5 x 103 ms-1. We discuss in chapter 2 how a rapidly diffusing probe (eg ammonia) can visit surface sites with a frequency high enough to intercept and react with the short lived oxygen states.
STM with in situ XPS enabled us to examine the novel chemistry we had observed earlier by surface spectroscopies. The model (see for example Fig 2.5) was scrutinised at the atom resolved level and the metastable oxygen states were observed at Cu(110) (Fig 4.11a). These states which we refer to as O?- (s) were shown to be highly reactive in ammonia oxidation and precursors to the inactive O2- (a) associated with the reconstructed (2x1)O state (see also Fig 5.5) thus confirming the model.
We also discuss supporting evidence (Chapter 5) obtained by Iwasawa (in 1995), Madix in (1996) and Conrad (in 1997) for metastable reactive oxygen states present at Cu(110) and Ag(110) at cryogenic temperatures and the precursors of the inactive O2- (a) of the reconstructed surface. However, we have no evidence concerning the precise charge associated with O?- (s). Presumably the isolated oxygen adatoms observed by the Fritz Haber group at Ru(0001) and Ag(100), Figures 4.16 and 4.19, have ’some’ electronic charge associated with them; we would likewise assign them as O?- (s) in keeping with the increase in work function associated with oxygen adatoms at metal surfaces. On a few occasions (e.g. p69) the reactive oxygen state was referred to as being "O- like". This was to draw attention to the strong similarity between the chemistry of O?- (s) - our model - and the reactivity reported by others of O- in homogeneous gas phase reactions with ammonia and hydrocarbons, and also of O- (a) in the chemisorbed state in heterogeneous catalysis.
The above is a summary of how our model was developed involving the metastable oxygen transient O?- (s) with translational kinetic energy and highly reactive. It became clear from discussions with Stephen Jenkins that his reservations had their origin in his view that hot electronic states were implicated in the model with (electronic) lifetimes of the order of picoseconds. This was not inherent to the model proposed for the surface reactions discussed in chapters 1,2,4 and 5.
If, however, the book and the reviewer have stimulated the reader to pursue the question of the (variable?) charge associated with the oxygen transients then we have achieved more than we anticipated.
P R Davies MRSC and M Wyn Roberts FRSC,
Cardiff, UK
Response from Stephen Jenkins
Since publication of my review, I have had the opportunity of corresponding fruitfully with both Philip Davies and Wyn Roberts on the nature of the ’hot’ adatom concept described in their book. As their current letter makes clear, their position is that such transient species are ’hot’ only in terms of the gross motion of their nuclei (a situation I described in my review as ’vibrationally hot’) but not in terms of their electronic configuration (ie they are not ’electronically hot’). Clearly this latter point differs from the understanding I had obtained whilst reading the book itself, and which informed the reservation expressed in my review.
I believe that the source of confusion originates with a notational issue: the authors label the hot transients with reference to their supposed charge state, either O?- or O- -like, in contradistinction to an inactive O2- species that they describe often as ’oxide’-like, but sometimes simply as a chemisorbed state. My belief at the time was that the authors intended to make an explicit statement as to the electronic configuration of the transient species, specifically that it was electronically distinct from a fully thermalised chemisorbed species; moreover, the instances where O- was employed led me to believe that a radical ion was implied, which situation is, in my view, likely to be literally possible at a metallic surface only for an electronically excited state. The charge-based notational practice (ie O?- or O- -like versus O2-) permeates the discussion of transients in several chapters throughout the book, and so the impression was created in the mind of this reviewer that a specific non-thermal electronic configuration was central to the concept, and that this was suggested to persist over a timescale comparable to the non-thermal nuclear motion. Since this picture evidently turns out not to have been the authors’ intention, my original reservation about the book’s message is resolved. The non-thermal nature of nuclear motion in the immediate aftermath of dissociation is an important topic, and the book amply demonstrates the role of STM in elucidating it (as my review noted). I do, however, feel that potential confusion would have been avoided if the notation chosen to denote the hot transient had not emphasised the charge state of the species. As the authors’ letter makes clear, and as my review glanced at, very little can yet be said with certainty about the precise charge state associated with the transient species, although first-principles calculations are beginning to offer at least a theoretical perspective on the matter.
Whilst noting the authors’ reference to the literature on hot transients, an area in which they have made seminal contributions, it is also fair to say that this aspect of surface reactivity has been much overlooked by mainstream surface science. Furthermore, the book’s target audience is described in the preface as including those new to the field, so prior familiarity with this literature cannot be assumed amongst the potential readership; the book does, of course, contain copious references to this literature, but my review was intended to cover the material directly presented, rather than the field as whole (i.e. judging the information imparted to me by the book per se, not the totality of what could have been gleaned by following up all of its many references). Whether confusion over the electronic aspects of the hot transient concept as described in this book will turn out to be general, or limited to this reviewer, remains to be seen.
It is entirely conceivable that aspects of my own recent theoretical work may have predisposed me to interpret charge-state notation more literally and interrogatively than the authors had intended: our density functional calculations had just revealed an intriguing vibrationally hot transient hydrotrioxy species formed upon reaction of ozone with a hydrogen-passivated silicon surface (see Fink and Jenkins, Surf. Sci. 602, L100 (2008)). In this instance, the transient species is predicted to be a true ground-state radical, which status is explicitly confirmed with reference to its charge and spin state; the distinction between this state of affairs and an electronically hot radical-like transient species was thus very much a concern of mine in the months immediately prior to viewing the book and writing my review. Notwithstanding these considerations, one very positive outcome of my discussions with the authors has been the inception of a promising dialogue over the possible future use of first-principles molecular dynamics to contribute to the further development of the hot transient concept.
S J Jenkins
Cambridge, UK
I agree most heartily with Katherine Haxton’s letter (Chemistry World, September 2008, p42). A lot of what she says about career metrics also applies to anyone who has undergone a career break for whatever reason, be that child rearing, illness etc.
I speak from an acknowledged position of self-interest, having suffered two brain haemorrhages, the first of which interrupted my PhD and the second a few months after my viva. The two year career break that the second entailed has finally caught up with me.
Following my illness (and concomitant career break) I returned to some semblance of a research career (part-time for the first three years). However, that career break has counted heavily against me when it has come to applying for fellowships or funding. Similarly, the break has caused me problems in securing a more permanent position.
Consequently, after a patchy postdoc career of about a decade, I have now been out of work for 20 months. I am probably going to have to leave science despite the fact that research was all that I ever wanted to do. I feel that I still have a lot to offer, but that science just doesn’t offer any viable career prospects for the vast majority of science graduates, let alone disabled scientists.
I am however extremely grateful to my colleagues at the University of York who have been very supportive in allowing me to undertake unpaid work in the Department of Biology which is effectively allowing me to retrain in web development and Java programming.
R Greaves MRSC,
By email
I support the opinions voiced by Katherine Haxton regarding the pressures facing young academics, but choose to remain anonymous in order to avoid possible reprisals. As a male 3rd year PhD student in a world-renowned institution I have encountered a narrow-minded working culture, bullying from academics, and continually feel that research is carried out as a competition for personal gain, not to further scientific understanding or for the benefit of society.
From my experience, this cut-throat culture (in chemistry departments) is not only a British problem as peers in other European countries have noticed similar attitudes. Furthermore, the macho culture is not just a turn-off for women (as noted in Chemistry World , August 2008, p8) but also to young male researchers who have a passion for science and a desire to work in a culture of openness rather than one-upmanship: factors that will be important when I consider my postdoctoral career.
Email supplied
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