A proposal to classify compounds and to establish water quality criteria based on laboratory data

ECOTOXlCOLOOY

AND

ENVIRONMENTAL

SAFETY

3, 126- 132 (1979)

A Proposal to Classify Compounds and to Establish Quality Criteria Based on Laboratory Data1 J. H. *National

Institute

of Public

CANTON*

AND

W. SLOOFF~

Health, Bilthoven;>&~titute Leidschendam, The Netherlands Received

A. A BASIC

August

Water

for

Water

Supply,

16, 1978

PHILOSOPHY

As in every industrialized and overpopulated country, in The Netherlands the aquatic ecosystems are still suffering from the large amounts of natural and xenobiotic compounds introduced in surface waters by man. Although the Dutch government has been successful in taking measures of sanitation concerning the emissions of some chemicals in surface water, still a lot of work has to be done before water pollution is reduced to an acceptable level. However, since The Netherlands is a rather small country, receiving waters like those of the rivers Rhine and Meuse which are already heavily polluted before entering The Netherlands, it becomes more and more obvious that national laws are inadequate and improper for proper water quality control and that international agreement in this matter is urgently needed. In this scope in the last few years some progress has been made, e.g., by means of the International Rhine Committee. Leaving aside such crucial matters as policing against the background of national priorities, it is evident that all decision makers need objective information on the harmful effects of water pollutants upon which to make judgments. Therefore pollution biologists must have quantitative data to prove that an exposure to a certain concentration of a compound will be ecologically safe to aquatic life. Although several procedures and philosophies for the use of bioassays as a guide in determining safe concentrations of toxicants for aquatic life have been proposed, there is still a reserved attitude toward using these to predict the consequences in complex natural environments. Of course, the factors that influence the harmfulness of a pollutant are numerous and often difficult to predict (e.g., pH, temperature, hardness, synergism, antagonism, addition, suspended matters, etc.). Nevertheless we have to face the fact that decisions cannot wait until they are based on incontrovertible scientific evidence. How to establish proposals for water quality criteria for aquatic pollutants in surface water with the purpose of protecting water organisms? First of all, a number of basic data are needed, e.g., the chemical structure of the compound, physical-chemical properties, levels in surface water or the amount of the pollutant to be released, data on the effects, and transport and 1 Paper presented mental Chemicals,”

at the meeting August 16-18,

0147-6513/79/020126-07$02.00/O Copyright All rights

0 1979 by Academic Press, Inc. of reproduction in any form reserved.

“Scientific Basis for the Ecotoxicological 1978, Vienna. 126

Assessment

of Environ-

COMPOUND

CLASSIFICATION

AND

WATER

QUALITY

CRITERIA

127

fate of the substance concerned. This means that first of all a compound should be tested on toxicity, persistency, and bioaccumulation. Bioassays have been used for many years and recently there has been a trend toward greater sophistication in the techniques. Formerly only acute tests were carried out, with death as the endpoint, but at present it is well known that such data have no predictive value for chronic exposures. Therefore many other effects should be observed too, including general health factors and behavioral and physiological effects. Since the purpose is to protect aquatic ecosystems, these effects should be studied on freshwater organisms of different trophic levels, e.g., bacteria, algae, crustaceans, fishes, and amphibians. However, life-cycle tests on all these species would be prohibitive with respect to both cost and time. Based on the conclusions of McKim (1977), that full-scale life-cycle tests with fish often did not give more information on the measure of toxicity of a toxicant than a 30-day test with fish in embryo-larval and early juvenile stages, it should be emphasized that such tests with early life stages are appropriate to reveal the concentration of a compound that will be of low risk, Insight into the accumulative behavior of a compound in water organisms is important as it can lead to a higher “toxic active” concentration in the organisms (species accumulation) or to a higher load by the intake of contaminated food (ecoaccumulation). This can be studied as shown in Fig. 1. Furthermore the persistency of a chemical has to be considered as an important factor in determining potential hazard, as persistent chemicals have the potential for wide dispersal in the environment. This property can be studied, e.g., by the “die-away” test (De Kreuk, 1976). Although very sophisticated and well-described techniques will be appropriate to reveal the toxic, accumulative, and persistentive character of a compound in general, some standardization or even a comparative tackling of these studies is needed to make an overall basic evaluation feasible. Fortunately some progress is made these days, e.g., by the International Organization for Standardization and the Organization for Economical Cooporation and Development. A predic-

FIGURE

1.

128

CANTON AND SLOOFF

tive toxicological judgment of a pollutant to protect aquatic life may be made with different objectives in mind: 1. From point of view of the compound, leading to classification in black- and grey-list compounds; 2. From point of view of the receiving surface waters, leading to water quality criteria; 3. From point of view of the wastes, leading to emission criteria. I. From Point of View of the Compound:

Classzfkation

In the framework of the treaty against chemical pollution of the Rhine River prepared by the earlier-mentioned International Rhine Committee, pollutants are divided into the so-called black- and grey-list substances. The principle behind these lists is that black-list substances should not be discharged in surface water at all and grey-list compounds have to be limited in discharge. It will be clear that for many pollutants the data to divide them in classes are often scarce or even not available. Nevertheless when we wish to proceed we have to use those limited data and try to classify the compound. In Table 1 a scheme is proposed in which data on short-term and long-term toxicity, bioaccumulation, and persistency are used, in order to classify the pollutants as black- and grey-list compounds. Since data on long-term toxicity are limited, often the acute LCSO values have to be used. It is suggested that when no reliable data on toxicity are available, TABLE PROPOSAL FOR CLASSIFICATION SOLELY

BASED

ON TOXICITY,

1

IN BLACK AND GREY LIST COMPOUNDS, PERSISTENCY, AND BIOACCUMULATION

Toxicity Short-term LC(EC)SO M-d) loo

>l

loo

Grey Grey Grey

Grey Grey Grey

Grey Grey Grey

COMPOUND

CLASSIFICATION

AND

WATER

QUALITY

CRITERIA

129

the substance should be classified as black for the moment. When a substance is a recognized carcinogen in or via the water, this substance should also be classified as a black-list compound. If the compounds of concern are suspected carcinogens and/or recognized mutagens it is not possible for the moment to indicate whether these compounds should be classified as black or grey. If data on persistency and/or bioaccumulation are lacking, the compound should be classified as black, except in case the toxicity is very low. To see whether this approach is useful in practice, we have classified approximately 100 substances for this moment. After dividing the compounds into these two classes the next step will be to set standards for the grey-list compounds. 2. From Point of View of the Receiving

Surface

Waters:

Water Quality

Criteria

Several authors have made suggestions to define the maximum concentration at which a chemical may be present in the aquatic environment without damaging its biota. In our view these suggestions have their limitations, because they are based on, for instance, very short exposure times, the use of one species and the use of just one criterion. We propose a so-called “ecological limit” (EL) which may be used to set water quality criteria. This ecological limit is based on the lowest “no-toxic-effect level” (NTEL) as can be indicated in toxicity studies with water organisms of different trophic levels, starting from the early life stages of the organisms. Only biological criteria are taken into consideration since other criteria may be more difficult to judge or to interpret. The slope of the dose-effect curve is important as the smaller the slope, the bigger the concentration range at which 0- 100% effect is expected. Therefore it is suggested that this dependency be expressed by dividing the EC25 by the EC50 and applying this quotient as a safety factor to the previously determined no-toxic-effect level. To come to the ecological limit the lowest NTEL x (EC2YEC50) value is chosen. 3. From Point of View of the Wastes:

Emission

Criteria

To derive emission criteria the water quality criteria can be used as the bases whereas the accumulative behavior and the persistency have to be considered as well. It is not possible to give an outlined procedure for establishing emission criteria since it depends, for instance, on the kind of discharge (single or continuous) and the local conditions of the receiving waters. B. SOME EXAMPLES To get an impression about the usefulness of the basic philosophy, a number of substances will be classified in black or grey lists and quality criteria will be proposed for two inorganic compounds.

130

CANTON

AND SLOOFF

1. Classijkation

In order to be able to classify a compound data on toxicity, persistency, and accumulation are needed. As model compounds the following substances were chosen: cr-hexachlorocyclohexane (a-HCH), pentachlorophenol (PCP), dinitroorthocresol (DNOC), dimethoate, omethoate, cadmium chloride (CdCl,), and sodium bromide (NaBr). The short-term toxicity tests were carried out with at least one representative of each trophic level (i.e., algae, crustaceans, and fishes) and in analogy to the concepts of the Dutch Standardization Institute. The results of the short-term toxicity tests are summarized in Table 2. TABLE RESULTS OF SHORT-TERM

TOXICITY

2 TESTS WITH SEVERAL COMPOUNDS

LC(EC)SO values (mg/liter) Test compound (r-HCH

Algae

Crustaceans

>lO

0.8

PCP

0.8-1.6

0.5

DNOC Dimethoate Omethoate

2 290 3,000 4.8 34,000

3.4 2.9 0.03 0.03

CdZ+

NaBr

8,800

Fishes 0.8-1.0 0.04-0.2 0.36-2.9 8.6-370 13-165 0.07-17 13,000-20,000

Toxicity class (mg/liter) -cl