Aerosol Sampling B

My first book, Aerosol Science: Sampling and Practice, was published by John Wiley & Sons, Ltd in1989. It had been conceived during a flight home to the United Kingdom from Australia in Decemberof 1987, the long hours of pondering and doodling producing an outline that subsequently changed littleas my notes evolved into a proposal and - ultimately - the book itself. Prior to that imposed period ofreflection I had had no intention whatsoever of ever undertaking the arduous task of writing a majorwork on the scale of a book. But it dawned on me that aerosol sampling was a central aspect of thestudy, characterization and surveillance of atmospheric environments and that it needed to be addressedscientifically in an integrated way in order that the results of aerosol sampling in the real world wouldhave any meaning. The book duly appeared at a time of burgeoning interest in aerosol sampling throughthe widening of the scope of health-related particle size-selective aerosol measurement, in particular theemergence of new criteria and standards, along with new instrumentation.The field of aerosol sampling has moved forward dramatically during the past two decades, andthe time has now come for a re-evaluation and update. A second edition was discussed. Eventually,however, it was decided - with the help of the publisher - that so much has changed, so much hashappened, so much is better understood, that a new book is in order. Although written from scratch,Aerosol Sampling: Science, Standards, Instrumentation and Applications nonetheless clearly retains itsorigins in the earlier book, covering much of the same ground in the earlier parts, albeit in a way that hamaturedover the years of consideration and reconsideration. It still separates out the largely scientificfrom the largely practical elements since this most clearly defines, and best integrates, the scope ofwhat has been achieved. In addition to a complete review of the latest science of aerosol sampling andthe development of new instrumentation, major new ingredients in the latest book include extendedchapters on aerosol sampling criteria and standards, new chapters on bioaerosols and direct-readinginstrumentation, and a whole new section on field methods and applications. The first book had itsorigins in aerosol sampling science as it related to occupational exposure assessment. This is hardlysurprising since, at the time, I was working at the Institute of Occupational Medicine in Edinburgh andmy research team was consumed on a day-to-day basis almost entirely with such issues. But my movein 1990 to the University of Minnesota, and then on to the University of Michigan in 1998, launchedme into the wider world of aerosols and aerosol measurement. So the new book presumes to providea comprehensive review of the whole field of aerosol sampling, aimed at scholars, occupational andenvironmental hygiene practitioners, epidemiologists, engineers and instrument developers involved inall aspects of the study, development and application of aerosol exposure assessment methods.A book like this demands a historical context, and I have attempted to provide one. It is an old clicheto say that ‘how can we work out where we are going if we do not know where we have been?’ Importantwork from the 1800s and early 1900s is referred to. Even Charles Darwin gets a mention. But the greatmajority of what is described comes from the explosion of interest in, and concerns about, occupationaand living environments in the period post World War II. Indeed, it may be said that it was this periodthat gave birth to the disciplines that we now know as occupational and environmental hygiene.Reading back what I have written, I see that the narrative in some respects has taken on the appearancof a ‘memoir’, not just by virtue of my own journey through the field over nearly three decades butalso through my associations with a large number of people who, too, were players in what has taken place. This book is really about them. It follows, therefore, that I owe a great deal to the many peoplewith whom I have interacted over the years. The list has to begin with C.N. Davies and W.H. Walton,the doyens of aerosol sampling science and its applications to aerosol exposure assessment. They hadbeen together at the chemical and biological warfare research establishment at Porton Down in Englandduring World War II, and had been among the pioneers of what we now know as aerosol science. Afterthe war, Norman Davies, with the new British Occupational Hygiene Society, founded the Annals ofOccupational Hygiene, bringing to it the strong scientific rigor that came from his academic groundingin physics. After Davies eventually moved on to found the Journal of Aerosol Science, Henry Waltontook over the Annals, adding his own background in physics to further enhance the reputation of thatjournal as the leader in the field of what we can now refer to as ‘occupational hygiene science’. Infact, it may safely be argued that Henry Walton was one of a small number of ground-breaking, true‘occupational hygiene scientists’, his contributions over time reaching beyond the physics of aerosolsand gases and into the realms of exposure assessment and occupational epidemiology. He was pivotal inthe development of aerosol sampling methods and exposure assessment in the context of coalworkers’pneumoconiosis during his years with the National Coal Board and latterly the Institute of OccupationalMedicine in Edinburgh. The obituary that appeared in The Scotsman after his passing in 2000 at thegrand age of 87 contained the words ‘It is not possible to estimate how many miners owe their livesand health to his innovations.’ There could have been no more appropriate epitaph. Henry Walton wasinstrumental in persuading me to come to the Institute of Occupational Medicine when he retired in1978, and that was the turning point that drew me into the field which is the subject of this book. Overthe years Ilearned that, in his inimitable quiet way, he had been the source of many ideas now taken forgranted in aerosol science, including the theories and development of aerosol dispersing devices suchas the spinning disc generator, respiratory protection devices and testing methods, and particle sizeselectivesampling devices such as horizontal and vertical elutriators. He was the driving force behind the definition and measurement of respirable aerosol and latterly - and less well-known - inhalableaerosol and porous foam filtration. After his retirement, Henry was a regular and welcome presence inthe Institute, and would often drop by my office for a ‘chat’. It was during one of these, for example,that he was finally able to convince me how it was possible for the aspiration efficiency of an aerosolsampler to actually exceed unity! I last saw him when I visited him to discuss revisions to a paper wehad written together for Aerosol Science and Technology on the history of occupational aerosol exposureassessment. It was a Saturday, the day of the funeral of Princess Diana, and his eyes were glued to thetelevision as the event unfolded. We did not speak and, after a while, I left him to his thoughts. But in duecourse the paper duly appeared, sadly the only time our names appeared together on the printed page.I am of course grateful to a very large number of others for their roles in my education about thescience and practice of aerosol sampling, most of whom feature - many frequently - as the pages areturned. There are those in my own research teams over the years, including my colleagues DavidMark, Alan Jones, Arthur Johnston, Rob Aitken, Harry Gibson and Gordon Lynch at the Institute ofOccupational Medicine; then - later - my faculty colleague Gurumurthy Ramachandran and doctoralstudents Perng-Jy Tsai, Mark Werner, Terry Spear and Avula Sreenath at the University of Minnesota;and subsequently my doctoral students Sam Paik, Wei-Chung Su, Laurie Brixey, Yi-Hsuan Wu andDarrah Sleeth at the University of Michigan. Then there are the scientists with whom I frequentlyinteracted, conversed, collaborated and shared research in Britain, including Richard C. Brown, SarahDunnett, Lee Kenny, Derek Ingham, Andrew Maynard, Trevor Ogden and Derek Stevens, to namejust a few. There are the many others in Europe and Scandinavia, including Lorenz Armbruster, PaulCourbon, Peter Gomer, Goran Lid￡n and Vittorio Prodi, and many others. I owe special words toYngvar Thomassen for providing me with frequent opportunities to expound my thoughts at the manyexcellent symposia he organized, always in wonderful locations, as well as for his steady stream of ideas and suggestions about how the results of all our researches could be applied in the real world. Ialso specially want to mention Jean-Francois Fabries. Paul Courbon introduced us over 25 years agoat an aerosols conference in Minneapolis, and we maintained scientific contact over all the years thatfollowed. He consistently made outstanding contributions to aerosol sampling science and its applicationsin occupational and environmental hygiene. It was a great loss to the whole aerosol science communitywhen this charming and modest colleague was taken from us prematurely only a few weeks before thisbook was completed after a long and brave battle with illnessUpon my arrival in the United States on a frigid New Year’s Eve in 1990, my work and interests inaerosol sampling began a new phase, with expanded new opportunities for the funding of research and forthe applications of what had been learned in the laboratory to field applications. I owe a special debt toBen Liu, Virgil Marple, David Pui, Peter McMurry and others who encouraged - indeed facilitated - mymove to the University of Minnesota, undoubtedly one of the ‘meccas’ of modem aerosol science. I amalso especially grateful for my long associations with Paul Baron, David Bartley, Nurtan Esmen, SergeyGrinshpun, Martin Harper, Bill Hinds, Mort Lippmann, Walter John, Mike McCawley, Bob Phalen,Klaus Willeke, and many others. There are at least two of these - you know who you are - where ourshared passion for music has exceeded even the joy of our scientific interactions! The work that some ofus carried out in the ACGIH Air Sampling Procedures Committee resulted in the important monograph,Particle Size-Selective Sampling for Particulate Air Contaminants that is widely considered a workingmodern framework for aerosol-related exposure standards.I am also grateful for my long associations with those in the various commercial enterpriseswho - along with names already mentioned - have been in the forefront of the realization of practicasampling instruments, including Debbie Dietrich, Bob Gussman, Pedro Lilienfeld, Eddie Salter, GilSem, and many others, including many that have kindly provided material for inclusion in this book.The names I have listed above are all my friends. Overall, the list of distinguished aerosol scientists,occupational and environmental hygiene practitioners, and engineers who have contributed to what Ihave learned, and hence what is described in this book, is long. Sadly, many will have been inadvertentlyoverlooked. To those who are not mentioned through my oversight, my thanks to you too and my sincereapologies. Of course, the actual writing of a book is only the first step in the process of bringing a work to fruition.In this case,in addition to all the individuals and organizations that provided various materials in theform of photographs and other pictures, I am especially indebted to the whole editorial and productionteam at John Wiley & Sons, Ltd, notably Jenny Cossham, Lynette James and Richard Davies and theirmany unnamed colleagues. I thank them all for their professionalism, patience and understandingFinally, it will be wryly noted by any reader who themselves have undertaken a large work that the effort involves many hundreds of hours in solitude. Why do we undertake such projects? It is hardly the search for immortality. That achievement is reserved only for the likes of Einstein and Newton. Foraerosol science, perhaps only Nikolai Fuchs has achieved that status. For the rest of us, the 99.999%we know that our contributions will fade soon after we have departed. What we hope for, therefore, is tobe able to integrate our knowledge in order to create a small new step in a field which can be the basisof further steps in the future by others. It is with this in mind that our thoughts tum to our families whohave been neglected so much for what might seem - ultimately - so little. In my case I am thereforegrateful to my children, Jeremy, David, Heather and Claire, now all grown up, for their encouragementof my ‘crazy’ endeavour. Most especially, it could not have happened without the ongoing love andsupport of my wife Christine. In her 11 years as my editorial assistant when I was co-editor-in-chief(with Gerhard Kasper) of the Journal of Aerosol Science, she came to know the names - and frequentlthe faces - of very many of those same aerosol scientists that are featured in the book. Now, althoughher memory falters prematurely, she still remembers most of them.