In recent years the Japanese economy has made rapid strides and progress as a result of the development and growth of numerous industries. One which has had considerable impact on the economic development of this country has been the heavy chemical industry. Unfortunately, however, the recent years have also witnessed an increase in discharged volumes of industrial and municipal wastes to such an extent that environmental pollution has come to be a problem of extremely serious proportions. This problem is illustrated in Table 1 and Figures 1 and 2 where annual changes in marine pollution which have been registered during the past six years in the coastal waters surrounding Japan are shown. The results clearly indicate that the highest numbers of registered cases of marine pollution have occurred in the vicinities of Tokyo Bay, Ise Bay, Osaka Bay and the Seto Inland Sea. In these four regions 1 486 cases were reported representing 63 percent of all reported cases on a nation-wide basis. Table 1 also demonstrates that pollution is on the rise in the coastal areas of Hokkaido and the Japan Sea. Classification according to source and type of marine pollution revealed that the majority of cases (84 percent) was due to oil and the next most important factor was the red tide (Figure 3). Industrial wastes totalled 64 950 000 tons of which 5 250 000 tons were acid and alkaline wastes, while 5 370 000 tons were due to dredging operations. Classification of the most frequent types of discharged industrial wastes dumped by vessels in 1974 are presented in Figure 4.
Geographic locations of fixed monitoring stations as well as pollutant dumping areas are shown in Figure 5; these stations and dumping areas were designated by the Maritime Safety Agency following a marine pollution survey which was conducted in and around the coastal waters of Japan. Water samples are collected twice yearly in summer and winter at the primary stations, and sea areas are divided into areas “A” and “B” in accordance with the Marine Pollution Prevention Law. Areas given the designation “A” are for the disposal of toxic chemicals such as mercury and cadmium, while those designated “B” serve as dumping sites for slag and metallic wastes. Samples of sea water and bottom sediments are collected annually in these areas for the analysis of COD, PCBs and heavy metals as part of a concerted monitoring programme.
A survey conducted in 1973 regarding the dispersion and landing of “waste oil balls” revealed that the regions of dispersion were more limited spatially than in a previous survey conducted in 1971; however, the problem still persists to a relatively wide extent. The results of the survey taken in 1973 also demonstrated that the concentration of petroleum hydrocarbons in the coastal waters of Japan was 0.02 ppm.
Diverse aspects of environmental pollution were evaluated in various surveys conducted in 1973. In the phase concerned with mercury contamination of some marine products, a total of 23 019 samples, including 22 403 of 303 marine species of fish and shellfish and 616 of plankters, were collected from 268 regions. Results demonstrated that 5 of 23 fish species from Minamata Bay, 5 of 28 species from Tokuyama Bay, 4 of 14 from the waterfront at Naoezu, and 5 of 19 from Kagoshima Bay exceeded the provisional control limit of 0.4 ppm total mercury. Furthermore, the mercury content of some freshwater species of fish taken from 9 rivers also exceeded the control limit. These results prompted the establishment of counter-measures aimed at controlling the mercury source, and operations for the removal of mercury-contaminated bottom sediments were concurrently implemented.
During the water quality phase of the survey 3 768 water samples taken from 634 water regions were examined. Of the total, 2 percent (76 samples) exceeded the environmental quality standard for total mercury; the results are summarized in Table 2.
In the phase of the survey concerned with bottom deposits, 5 186 samples were collected from 635 stations, of which 2.3 percent (120 samples from 25 stations) were found to exceed the provisional mercury standard (25 μg/g) for bottom deposits. In Table 3 areas are listed where eradication measures were instigated in order to promptly decontaminate the bottom deposits. Clean-up procedures have been implemented in most of the problematic areas. On 30 September 1974 environmental quality standards for water were established at “less than 0.0005 ppm” for total mercury, and “not detectable” for alkyl mercury.
A nation-wide survey of PCBs and agricultural chemicals was conducted in the regions of the sea surrounding Japan in 1972 and 1973. As shown in Table 4, 3 369 samples representing fish and shellfish were collected from 20 stations. Based on the results, guidelines were drawn up in order to ensure self-restraint in the operation of the fisheries industry.
The water quality phase of the survey examined 1 281 samples originating from a total of 282 aquatic regions, including those from 208 rivers, 28 harbours and 46 marine areas where sediments were found to contain PCBs at concentrations exceeding 1 ppm. The results are summarized in Table 5.
In the phase of the survey dealing with bottom deposits, a total of 1 789 samples were collected from 354 aquatic regions, which included 258 rivers, 38 ports and harbours and 58 marine areas. The results are presented in Table 6 and demonstrate that the sediments of 51 bodies of water exceeded the provisional control level for PCBs (10 ppm on a dry weight basis). Moreover, the number of aquatic regions in which the maximum concentration of PCBs either exceeded 100 ppm, ranged from 50 to 100 ppm, ranged from 25 to 50 ppm, or was less than 25 ppm, were 6, 8, 11 and 26, respectively. Removal of contaminated sediments in those areas which exceeded the provisional standards was considered to be urgently necessary; in some regions, such measures have already been finalized. The organochlorinated compounds, represented by DDT, BHC and dieldrin, illustrate this need for removal. Due to the fact that these compounds tend to remain in foodstuffs and in the environment as residues, extremely stringent restrictions and limitations on their use were enacted and enforced in 1971. Up until that year cases had been reported of marketed farm crops which contained dieldrin, DDT, etc. in quantities exceeding the residue standards for agricultural chemicals. Very few cases have been reported in recent years. Nevertheless, proof that significant residual quantities of these chemicals continue to persist in the environment has been demonstrated by the high concentrations of BHC, DDT and dieldrin detected in the bodies of birds inhabiting the region of the Seto Inland Sea during the period 1972 to 1973. This has been particularly striking among carnivorous species which inhabit beaches.
The current situation regarding regulation of the utilization of agricultural chemicals is presented in Table 7. Safety standards have been enforced to protect marine animals from pollution due to 54 different chemicals including CVP and PCB.
Finally, a recent characteristic of water pollution is its spread into coastal waters due to an increase in the influx of waste water discharge originating both from industrial and domestic sources in newly-developing urban areas. In those bodies of water which are partially enclosed, eutrophication problems arise as the result of the influx of nitrogen- and phosphorus-containing materials in addition to the problems created by organic matter. Values reflecting chemical oxygen demand (COD) for some important lakes and bays in Japan are presented in Figure 6 as some indication of the state of water pollution in this country.