あおぞら財団 The Role of Epidemiology in Japan’s  Pollution Litigation, and the Extent of Its Progress
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The Role of Epidemiology in Japan’s Pollution Litigation, and the Extent of Its Progress

by Katsuji Mineta
Lawyer

1. Epidemiology and the Struggle Against the Unknown Cause Argument

Even in the countries known as “advanced,” we have always heard people dogmatically conclude that social phenomena such as pollution and pharmacological damage have unknown causes, and we still hear this sort of argument. If something’s cause is unknown, no action can be taken to deal with it, and we cannot respond to the demands for redress from the sufferers.

In Japan too, doing battle with the unknown cause argument has been a major challenge to the victims of Minamata disease, subacute myelo-optico neuropathy (SMON), respiratory disorders, and the like. This argument always works to the advantage of those who cause damage, and to the disadvantage of the victims, and because the offender is in all cases a socially powerful group, or the government itself, the victims’ battle with the unknown cause argument is a terribly arduous one.

Epidemiology is one means of beating this argument. Japan’s pollution lawsuits too have made progress by employing this means.

Here I shall explain the use of epidemiology in Japan in terms of cause (causality) as regards air pollution and the respiratory organs.

2. The Yokkaichi Pollution Struggle and the Epidemiological Causality Argument

In Japan, Yokkaichi air pollution was the first instance of frequently occurring pollution-caused respiratory disorders (such as bronchial asthma, chronic bronchitis, emphysema, and asthmatic bronchitis), and the first real battle to determine responsibility. From about 1955 a petrochemical industrial complex including a thermal power plant began operations in Yokkaichi, and when it started full-blown operation in about 1960, many people living around the complex suffered respiratory ailments.

They suffered from what came to be called Yokkaichi asthma, and there were many cases of not only bronchial asthma, but also a broad array of respiratory disorders. Needless to say, respiratory disorders like bronchial asthma sometimes occur with no connection to air pollution, and are ordinary phenomena.

But this became a social issue because so many more people than usual were coming down with respiratory ailments, and this spawned controversy over the cause, who was to be blamed, and redress for the sufferers. Of course here too the unknown cause argument made its power felt, and remedial measures were delayed.

The breakthrough here was an epidemiological study that analyzed the relation between the number of people seeking treatment for respiratory ailments under national health insurance, and the concentration of atmospheric sulfur dioxide. This study demonstrated high numbers of patients with respiratory ailments in regions with high SO2 concentrations, and showed that the higher the SO2 concentration in a region, the more people had respiratory ailments. The study had confirmed that the social phenomenon (prevalence) of many respiratory ailment sufferers in Yokkaichi City was due to atmospheric SO2, and clearly showed that responsibility lay with the companies in the complex, which emitted much SO2. Later there was progress in developing methods, and there was a growing body of research from epidemiological studies. These confirmed the early research results.

Based on these achievements, programs for paying air pollution victims’ medical expenses started in 1969 in Yokkaichi and other places, and the 1972 decision in the Yokkaichi pollution lawsuit’s finding was that the SO2 emissions from the complex companies had caused respiratory ailments in the Yokkaichi area. Owing to this outcome, the Pollution-Related Health Damage Compensation Law was enacted in 1973, which opened the way to total redress for air pollution victims. The Yokkaichi Air Pollution Lawsuit had been filed in 1967; the landmark 1972 decision had found that six complex companies were jointly responsible, and ordered them to pay compensation. This contributed greatly to the Nishiyodogawa Lawsuit and to subsequent litigation over pollution and drug-induced damage, and as such it recognized epidemiological causality as a powerful methodology for having causality legally acknowledged.

3. Epidemiology’s Methodology and Epidemiological Causality

Epidemiology is defined as research and and other investigation on the factors that determine the frequency and distribution of diseases in human groups. As such, it is a science that observes groups of people, notes the distribution and frequency of disease, and looks for the factors that determine that distribution, and for a disease’s cause. In the nineteenth century when there were epidemics of contagious diseases, Robert Koch researched the frequency with which cholera arose and how it is communicated; before discovering the cholera bacterium he found that it spreads by well water, and worked to suppress the epidemic. This too was an achievement of epidemiology.

Let’s see how it works, specifically in terms of air pollution epidemiology. First, we see that respiratory illnesses are more prevalent in some places than others, which constitutes an unequal distribution. We look for differing frequencies of respiratory ailments for each factor (for example, age, sex, allergy, smoking rate, extent of air pollution, and occupation), including host, cause, and environment, that could possibly determine such an uneven regional distribution, and which is related directly or indirectly to the ailment’s outbreak. If there is no difference in frequency in areas with the same extent of air pollution, then air pollution could be a hypothetical epidemiological factor that possibly determines the high incidence of respiratory illness.

If there is said to be a statistical connection between the hypothetical cause (air pollution) thus put forth and the result (the frequency of respiratory ailments), then the following conditions and other items are considered, and epidemiological causality is inferred. The conditions are those used by a council for the U.S. public health bureau director to investigate smoking and health. Not all must be satisfied.

(1) Universality of relevance (the same relevance is found in studies of other groups); (2) soundness of relevance (a condition showing the soundness of statistical relevancy; there is strong relevance if a quantitative reaction relationship is found); (3) specificity of relevance (meaning there is a specific relation between a certain cause and an effect); (4) temporality of relevance (causes were in place before effects appeared); and (5) consistency of relevance (if there is said to be causality between a cause and effect, this must be consistent with existing knowledge).

It is therefore epidemiological causality that observes groups of people and infers causality, while experimental epidemiology is sometimes used to confirm causality. In the Yokkaichi City Pollution Lawsuit, and in the Nishiyodogawa Air Pollution Lawsuit that we handled, the results of research employing this procedure are bringing about a recognition of epidemiological causality between air pollution (especially pollutants like SO2 and particulates) and respiratory disorders such as bronchial asthma.

In court one is required to prove causality, which is necessary from a legal perspective, but in addition to the historical facts on air pollution and how it causes damage, the fact that such epidemiological causality has been scientifically demonstrated has sufficiently proved legal causality. Surely it is this thinking that has assured progress in dealing with pollution sources and providing redress for victims on the basis of their court victories and the victorious court decisions in the pollution and drug-caused health damage lawsuits in today’s Japan. The causes of health damage are definitely not unknown.

4. Progress in Air Pollution Epidemiology

Air pollution epidemiology’s method is cause comparison studies that assume air pollution as the hypothetical cause, and make comparisons, according to differences in the extent of air pollution, of the rate of people showing symptoms of disorders such as chronic bronchitis, persistent coughs and phlegm, and asthma-like symptoms (current) in groups of people living in studied areas. To perform studies of symptom rates, there are internationally established means including the BMRC and ATS.DLD questionnaires.

In the measurements of air pollution concentration, it is now becoming possible to take continuous readings of representative pollutants including SO2, NO2, and particulates. But there is still no system for measuring the particulates in motor vehicle — especially diesel — exhaust, which is an issue now.

The new challenge regarding air pollution in Japan is to determine the health impacts of motor vehicle exhaust along roads. For that purpose we will need epidemiological studies, a system for measurements, laboratory animal experiments, and other means focused on motor vehicle exhaust.