Encyclopedia of Environmental Science and Engineering, Volume I and II

EPIDEMIOLOGY 387

in life tables (RMLT), the name given to it by the originator,

D. R. Cox, or as the proportional-hazards model. Essentially

it is a form of multiple regression analysis, into which it is

incorporated as many as possible of the variants that dis-

tinguish the workers in the factory: sex, age, race, duration

of employment, type of job, area of work, exposure levels,

etc. The comparisons are then made within the factory itself,

so that the workers in an area of potential hazard are evalu-

ated against the experience of the rest of the factory, taking

into account all those factors included in the regression and

likely to infl uence the behavior of each individual. Because

of its independence of any external standard as a basis for the

control, this method has a clear advantage over other kinds

of comparisons. Its disadvantages stem from mainly infor-

mation required, and an adequate varied range of areas of

work. Given the requisite data, it provides probably the most

powerful form of epidemiological analysis in this fi eld.

SOME OTHER APPLICATIONS OF EPIDEMIOLOGY

The methods of epidemiology are increasingly being used

in the investigation of a wide variety of health defi ciencies

or of areas of group ill health. The study of the relationship

between Legionnaires’ disease and defective maintenance

of air-conditioning plants owes much to such methods.

Another example, not fully worked out, is that of the sick-

building syndrome, where a number of symptoms of mal-

aise, together with respiratory and eye affl ictions, have been

related to ventilation problems and lighting conditions in

some kinds of modern buildings. Incidents of food poison-

ing have been among the “classical” applications of methods

perhaps more akin to those of crime detection than a strictly

epidemiological type. More recently studies of outbreaks of

food-borne disease—some due to inadequate cooking, some

to the increased demand for precooked convenience foods,

some to more intensive animal husbandry and processing of

the meat—have made extensive use of methods of epidemio-

logical analysis. Other obvious areas of application include

inquiries into sudden outbreaks of other forms of disease,

especially when localized in time or space, and the study of

road accidents, whether in general or of specifi c “hot spots.”

CONFIDENTIALITY

The usefulness of epidemiology, whether in its descriptive or

analytical manifestation, depends essentially on the extent

and consistency of the data on which it is based. A current

trend in a number of countries has been that of “data pro-

tection,” ostensibly to protect the privacy of the individual,

and resulting in the “anonymization” of many data items.

For a great many, if not all, items of information concern-

ing an individual, the name is the most useful identifi cation

to link them together. Consequently the movement toward

data protection has been against the interests of epidemiol-

ogy, and has hampered much of its development. In many of

the countries of Europe a residue of the Code of Napoleon

has made the link between the cause of death and the name

of the deceased an item of strict confi dentiality, so that the

death certifi cate is in two parts: a statement of the fact of

death of a named individual, for legal purposes, and a sep-

arate statement of the cause(s) of death of an anonymous

person, of stated sex, age, and race, for purposes of prepa-

ration of the country’s mortality statistics. Consequently,

epidemiological study has been considerably hindered by

this dissociation. It is ironic, therefore, that whereas in those

countries there have been attempts to liberalize this restric-

tion in the interest of useful epidemiological studies, the

reverse has been the trend in some countries where access

to such data has previously been unrestricted. It should be

possible to devise a compromise that permits suitably moti-

vated and qualifi ed investigators to obtain free access to all

data necessary to their study without jeopardizing the gen-

eral right of the individual to the confi dentiality of the data

concerning himself.

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