The exa ct nature of the discipline is hard to describe exactly. It has roots in both science and m edicine, (Ballantyne, Marrs and Turner 1993C, p 3) referring to it as ‘a recognized scientific a nd m edical discipline' [my italics].
However, while its scientific qualities are not in doubt, it is clear that, particularly in the aspect of toxicity testing and hazard assessment, that scope still exists for professional judgem ent, based on expertise and experience: ‘That toxicology is not an exact science has b e co m e a cliché am ong its practitioners. Notwithstanding the detailed descriptions of experimental conditions and procedures prom ulgated under the heading of “ guidelines", the options and leeways open to the investigator ore so numerous that no two studies of a given substance in laboratories of "equal c o m p e te n ce " turn out to be exactly the same' (Oser 1987). This has led to the assertion that m odern toxicology may still be said to be both an art and a science (Gallo 1996), by contrast with some other disciplines, for exam ple chemistry (Knight 1992), which have progressed steadily over time aw ay from qualitative art and towards quantitative science. For comparison, contrasting views exist ab o u t the nature of m edicine, which is seem by some to be both an art and a science (Morrell 2000), and by others to hove largely moved from art to science (Azzone 1998).
Like m any other contem porary sciences, toxicology is continually changing and developing in terms of techniques and concepts; Weiss and Cory-Slechta (1994) suggest that some com ponents of contem porary toxicology are undergoing almost continuous change.
Toxicology clearly has both pure and applied aspects, and overlaps with m any other disciplines, ‘encompassing a very large number of basic and app lied issues'
(Ballantyne, Marrs and Turnerl993C, p3). There are two clear, albeit inter-related ‘strands' within toxicology: the 'pure' research aspect, aim ed a t elucidating toxic mechanisms and similar factors, and the ‘toxicity testing' aspect, aim ed a t producing realistic estimates of potential harm.
Freiss (1995) argues that toxicological research, aiming a t protection of human health from adverse effects of chemicals (arguably an over-restrictive definition of the subject), has a logical sequence of five stages:
• projection or extrapolation of animal d a ta to prediction of effe ct on exposed tiuman populations
• validation of prediction of human effects by epidem iological studies of exposed human populations
• for validated effects, developm ent of quantitative measures of p otency via im portant routes of human exposure
• developm ent of quantitative measures of the risks of specific toxic effects in humans under specified exposure conditions
Freiss goes on to argue that these steps involve two major, and different, forms of scientific and technical effort:
• scientific, encompassing the experimental generation of the database, followed by extrapolation or prediction of im pact on humans
• m ethodological, estimating intrinsic potency and human intake dosage, to yield estimates of risk
Freiss refers to these two steps as toxicological evaluation and risk assessment, respectively, and notes that they are typically carried out by two communities of technical specialists who differ markedly in their training, experience, m anda te and priorities. He denotes these two kinds of toxicologist os research specialists and risk assessment/management specialists, and argues that a more successful interaction betw een them is essential in generating the most useful toxicological d a ta , and making best use of it.
Gallo (1996 p 6) sees these aspects as defining some unique characteristics of toxicology: ‘The history of m any sciences represents an orderly transition based on theory, hypothesis testing, and synthesis of new ideas. Toxicology, as a gathering and an app lied science, has, by contrast, developed in fits and starts. Toxicology calls on almost all the basic sciences to test its hypotheses. This fact, coup led with the health and o ccup ationa l regulations that have driven toxicology research since 1900, has m ade this discipline exceptional in the history of science.' He also suggests that toxicology may be unique in ‘pointing’ to both basic sciences and direct applications a t the same time.
Forensic science is a more extreme example than toxicology, involving a very broad base of scientific and technical disciplines. It is 'essentially the app lication of scientific methods and techniques to matters involving the public: that covers a lot of ground.
Every science from chemistry to medicine, from biology to statistics, from dentistry to anthropology, can be a forensic science, it it has some application to the law or public matter' (Siegel, Saukko and Knupte, 2000). Lee (2000) emphasises this diversity: 'Forensic science is always a diverse field, built on the principles ot chemistry, biology and physics, and incorporating countless other specialities. Today, the service ottered under the guise ot "forensic science" includes specialities from virtually all aspects ot modern science, medicine, engineering, m athematics and technology. For those working within some area [ot torensics] it is nearly impossible to m aintain even a cursory level ot knowledge regarding all available subcomponents within forensic science.' In addition to these scientific and technical aspects, legal and procedural matters, such as docum entation ot evidence, are ot great im portance (Eckert 1997).
This science is therefore much more multi-disciplinary than toxicology, which rests upon a more limited base ot chem ical and biom edical science, albeit with a
regulatory and legal dimension. To a greater extent than toxicology, forensic science can best be understood, in Hirst's terms, os a field ot study (see later section).
Virtually all writers note that toxicology is multi-disciplinary - ‘a major multidisciplinary science' (Oser 1987), ‘a multi-disciplinary science .. a multi-disciplinary fie ld ’ (Loomis
1978), but the exact nature ot the disciplinary mixing is subtle. Koeman ( 1996, p 7) carefully defines that:
‘Toxicology is typically a mulfidisciplinary field ot science, which, to on increasing extent, assumes the character ot an interdiscipline. This implies that the integration ot various disciplines in toxicology not only means that the various sciences are applied simultaneously, but also that integration poses its own specific problems' [author's italics].
A similar view is expressed in the 1998 information pack tor the gradu ate toxicology program m e ot the University ot Rochester (New York): ‘By its nature, toxicology is highly interdisciplinary. It combines the knowledge base and approaches ot such fields os physiology, pharm acology, psychology, biochemistry and m olecular biology, to address fundam ental questions regarding the mechanistic effects ot chemicals on living organisms.'
The editors ot a major m onograph (Sipes, McQueen and G andolti 1997) suggest that toxicology ‘is the scientific discipline that combines the elements ot chemistry and biology. It not only addresses how chemicals a ffe ct biological systems, but how
biological systems a ffe c t chemicals. Due to this brood definition, toxicology has always been an interdisciplinary science. It uses advances m ade in other disciplines to better describe a toxic event or to elucidate the mechanism of a toxic event.’
(This seems to suggest that as a com bination of chemistry and biology, toxicology equates to biochemistry; this is not the case, as is clarified later in this section. Toxicology encompasses many more disciplines than merely biochemistry).
We ca n take this to m ean that there is a single interdisciplinary subject called toxicology; this will have its own knowledge base, and its own set of concepts and methods. However, w e must also recognise that much of toxicology makes direct use of knowledge, concepts and methods from other disciplines. These considerations will have considerable implications for information and com m unication, as will be
discussed later.
It is worth going a little further along this line, to enquire into the nature of toxicology. To do so, it will be helpful to use the idea of Paul Hirst, the philosopher of education, on the ‘forms of knowledge (Hirst 1974, Walsh 1993). Drawing ultimately on the ideas of the Greek philosophers, particular Aristotle, Hirst proposes that all know ledge and understanding m ay be logically lo cata ble within a finite number of domains. These domains, or categories, ore to be distinguished by four criteria:
• central concepts peculiar in character to that form (e.g. "number" in mathematics, "mass" in physical sciences, "sin" in theology)
• a distinctive logical structure (m athem atical concepts and symbols are related in very different w a y to statements of religious belief)
• distinctive forms of expressions, testable by distinctive criteria (tests of validity are very different in physical science from those in literary criticism, and the logical deduction of m athematics is different from the em pirical verification of physical science)
• a collection of particular skills and techniques, developed for the particular form of knowledge to be handled (although he regards this criterion as less im portant that the other three).
Where these criteria are violated, w h at results is not a new dom ain, but nonsense; the statements that "m agnetic fields are angry" or that "cardinal numbers are holy" can have no meaning, beyond [perhaps] the m etaphorical.
Hirst proposes that there are seven such domains, or "forms o f knowledge". These are: mathematics; physical sciences; human sciences; literature and the fine arts; morality; religion; philosophy. They are sometimes stated equivalently as: logico-m athem atical; empirical; interpersonal; aesthetic; moral; religious; philosophical. In earlier versions of his theory, history and social sciences were also treated as indepe nden t forms, but are not generally so regarded.
A ca d e m ic subjects may then be m appe d onto these forms. Sometimes they will correspond exactly; m athematics and philosophy, for example, are forms directly identifiable with subject areas and a ca d e m ic courses. These same forms m ay also be basic to other discrete subject areas, of course: mathematics for theoretical physics and econometrics, for example. More commonly, a discrete subject area falls, along with m any others, as an exam ple of a form. Hirst's formalism gives no help in deciding the boundaries and scope of a subject; w e may agree that physics and chemistry are both examples of the physical science form, but this does not help us to d e cid e where the areas overlap, nor w h a t is chem ical physics and w h at physical chemistry. Hirst sees these forms of knowledge os equating to disciplines conce rn ed with validating one logically distinct form of expression of knowledge, by developing one particular w ay of structuring experience.
• In proposing such forms. Hirst regards knowledge os falling into three types; prepositional knowledge, "knowing that"
• procedural knowledge, "knowing how"
• knowledge by acquaintance, "direct knowledge"
Whilst his theory was originally propounded on the basis of the suprem acy of prepositional knowledge (Hirst 1974), Hirst subsequently revised his views to take a cc o u n t of the extent to w hich prepositional knowledge is, in fact, based on procedure, theory relates to "know how", and the forms may be seen as a rarefied description of practice (Walsh 1993).
Nonetheless the forms and associated disciplines, as stated, a p p e a r as entirely "pure" theoretically-oriented topics. Hirst recognises a second con ce p t; a "practical
discipline" based on one of the forms, but oriented towards solving practical problems. Engineering, and its various sub-branches, for example, is clearly a practical discipline based upon the form of physical science.
Beyond this. Hirst recognises that there are some a ca d e m ic subjects, pure and
applied, which do not fit neatly into one of these forms. The reason is simply that such subjects do not share the concerns of the disciplines noted above; rather they are focused on their subject matter, drawing on all forms of knowledge which contribute to them. Hirst refers to these as "fields of study"; multi-disciplinary in nature, and given coherence, not by adherence to a single form of knowledge and m ode of discourse, but by a focus on a com m on central topic. By contrast with the forms of knowledge, which Hirst considers finite in number, these fields, composite second-order
constructions, m ay be formed as convenient, and are not limited in number; they expand as knowledge itself expands. The main example which Hirst gives in introducing this c o n c e p t is geography, where the central focus of humanity in the environment is studied using the methods and languages associated with several forms.
Considering toxicology in the light of these ideas, it seems that there are two ways in which toxicology m ay be viewed. Most practising toxicologists would presumably regard the subject as falling within the ‘physical sciences / em pirical' form. Since, as w e have seen, toxicology has a strong practical aspect, it should be viewed as a
‘practical discipline'. An alternative view could be taken, based on the im p a c t of social, political and ethical issues on the science. If these are a c c e p te d as a part of toxicology, then it could be argued that the subject would be better treated as a
‘field of study', whose focus of interest is the harmful effects of substances on organisms and ways of dealing with them. This inclusive definition would certainly incorporate all forms of studies, views and writings dealing with all aspects of toxicology, and from all perspectives. However, it is probably more realistic, considering the nature of most toxicology literature, and the concerns of most toxicologists, to prefer the scientific ‘practical discipline' definition.
We con therefore conclude that toxicology is a practical discipline, within the form of the em pirical natural sciences, while showing some of the characteristics of a more general ‘field of study'.