«: AGROCHEMICALS: FATE IN FOOD AND THE ENVIRONMENT PROCEEDINGS OF A SYMPOSIUM, ROME, 7 - 1 1 JUNE 1982 JOINTLY ORGANIZED BY IAEA AND FAO l^J I N T E R ...»
In collaboration with the inventors, synthesis o f the tritium 3 H-labelled compound was done; as indicated in the formula (Fig. 1), tritium was incorporated in the 3, 3 ' a n d 5,5'positions.
The specific radioactivity was 69.5 mCi/g and the prepared quantity o f compound was 5.375 g, to which were added 2.687 g o f sodium bicarbonate. 1 The trial compound was coded ALAC-II. A 4-year old 'pie noire' cow of 450 kg received a single dose in 3 gelatine capsules, each containing one-third o f the ALAC-II- 3 H bicarbonate mixture. The amount administered corresponded to the usual therapeutic dose for cows (1.2 g ALAC-II/100 kg b o d y weight).
Faecal and urinary excretion, secretion into milk and concentration in blood were monitored for 14 d after administration. Fourteen days after administration the c o w was slaughtered and distribution in different organs and tissues (liver, meat, kidney, spleen, fat, bone marrow, brain, bile) was determined.
Figure 2 shows that maximum concentrations are reached in blood and urine approximately 48 h after administration and in milk 72 h after administration and that these concentrations decrease by half-life times o f 1 d (urine, b l o o d ) and 4 d (milk) between days 3 and 9.
Concentrations o f the compound in different tissues and organs at sacrifice are given in Table I. Recovery and distribution are given in Table II.
Fourteen days after administration recovery was quite good and various organs and tissues contained less than 1% o f the administered dose. The highest concentration was observed in the liver ( 5. 4 2 ± 0.06 mg/kg); bile fluid, kidneys, spleen and muscle showed lower concentrations.
On the last day o f the Symposium a Panel Discussion was held on the Research Needs for Effective and Safe Pesticides in Developing Countries. Preliminary remarks were made by scientists from Brazil, the Federal Republic of Germany, India, the Philippines and the United Kingdom, followed by a lively discussion on the topic which continued for one and one-half hours. The following is a brief résumé o f the Panel Discussion, as interpreted by the Scientific Secretary o f the Symposium.
The need for appropriate use o f pesticides to improve f o o d production was pointed out repeatedly. A number o f scientists also noted that the most effective way to increase f o o d production is to intensify agricultural production, which implies increased investment in all aspects o f production and protection. This increase in investment must be protected by the appropriate use o f pesticides.
Thus, use o f pesticides will increase, particularly in developing countries where it is currently rather limited.
The most consistent comment throughout the discussion was that great differences exist between nations which influence research priorities in relation to pesticides. These differences are not limited only to those between developed and developing countries, even though this was the one most frequently mentioned.
Differences in climate (e.g. between tropical and temperate zone agriculture) affect the fate o f pesticides, so that in at least some and perhaps many cases the residues in soil, water and foodstuffs will be very different after the same usage patterns. Certain data indicate that some chlorinated hydrocarbon pesticides do not appear to be as environment damaging in tropical climates as in temperate ones. However, these differences have not been investigated sufficiently to allow definitive statements about the fate o f some o f the more long-residual pesticides, such as chlorinated hydrocarbons.
Another dissimilarity mentioned was that in some cases priorities were established by governments o f developing countries regarding pesticide usage and pesticide residues which did not coincide with the priorities set by governments in developed countries. These priorities should be recognized as having been set by government authorities who have taken into account such things as levels o f education and training o f their farmers, economic conditions o f the country and o f the farmers, and availability o f trained research scientists and equipment and facilities with which to carry out the research. Economics was repeatedly pointed out as one o f the major deterrents to substituting some o f the newer, more expensive pesticides for some o f the older and cheaper ones, many o f which have been severely restricted or banned in developed countries.
It was mentioned that the pesticide formulations available in many developing countries are the same ones used in developed countries. This has resulted in occasional failures o f the pesticide to effectively control the pest because the
formulation available was not designed for the tropics, for high rainfall, etc.
In turn more pesticides are used and, thus, a potential for higher pesticide residues ensues.
Several speakers mentioned the possibility of establishing regional centres for pesticide research, using similar climatic zones as regions. These centres would conduct research on the primary pesticides used in the region, including the fate of pesticides and residues. This information would then be available to interested governments and organizations.
The ever expanding need for trained people was repeatedly emphasized and pleas were made to increase the amount o f training available for scientists from developing countries. Requirements include not only technical training but also training for technicians, electronics equipment maintenance personnel, and others.
The need for better library facilities and reprint exchanges was also stressed.
The specific types o f research required for the development o f effective and safe pesticides in developing countries, which require or will greatly benefit.from
the use o f radiolabeled pesticides, include the following:
(1 ) Adaptive research to seek ways o f using existing pesticides effectively, efficiently and safely under local conditions (2) Special studies aimed at evaluating the actual risk o f using the older, more established pesticides, such as DDT, under tropical conditions (3) Studies to improve pesticide formulations (4) Studies to improve methods o f application (5) Studies aimed at determining the potential problems associated with pesticides moving into aquatic systems in which fish and other f o o d are being produced (6) Specific pesticide research aimed at solving pest problems and pesticide residue problems for intensive agricultural production, such as multicropping and no-till agriculture.
There was no question that more pesticide research is needed in developing countries. Governmental authorities should establish national priorities for the types o f pesticide research required to solve local problems. Experiments using isotopically labelled pesticides can be a great assistance in solving many specific pesticide problems in developing countries.
HIGHLIGHTS OF THE CONFERENCEK.A. L O R D United Kingdom REVIEW A wealth o f information has been produced to illuminate many aspects o f the use o f agrochemicals and their effects on the environment.
Perhaps the major highlight o f the Symposium was the conception o f a programme that brought together so many differing aspects of the fate and behaviour o f agrochemicals in the environment. The very breadth o f the programme was bold, including the importance of raising agricultural output to feed the growing world population, with other topics ranging from the cost o f safety in terms o f finance or lost potential for producing f o o d, to the development o f techniques to study problems. All play an important and interacting part.
One might possibly draw an analogy between the various facets o f the use o f agrochemicals and some o f the aqueous ecosystems described during the Symposium. For example, in some conditions distinct communities o f algae, differing in their sources o f nitrogen, may exist in zones in lakes, but use of a barrier (container) to isolate part o f the water for experimental purposes significantly changes the conditions. Movement o f nitrogen and other chemicals is prevented, and the results o f measurements, while important, have a different significance from any made in the absence of restraints. Lakes and other bodies o f water themselves receive water from land bearing material which affects the aquatic environment. Some substances are naturally occurring, others may be agrochemicals that disturb the ecosystem, either by providing additional nutrients or by toxic effects.
There was much emphasis on the so-called bound residues. These are not easily defined with precision but represent potentially biologically active materials not readily assayed because they are difficult to separate from the surrounding matrix.
Evidence was presented o f the degradation o f pesticides in soil being affected by inorganic and organic fertilizers and materials providing ready carbon sources for microbial growth. Both increased and decreased degradation were observed and there was evidence o f different metabolic end-points, indicating changes in metabolic pathways and possibly soil microbial populations.
Despite emphasis on the results o f investigations and their significance, development o f new applications and possible pitfalls in the use o f nuclides were not neglected, although nuclear techniques are established and accepted as making important and unique contributions to the study o f agrochemicals in the environment. There were elegant illustrations o f combining techniques to show both movement and degradation by using the results from specific gas chromatographic determination o f the parent compound and tracer techniques to measure the total material. At the same time the work illustrated the ability o f glass vessels to adsorb and degrade materials, a property which may cause misleading results.
There was a forceful reminder o f the value o f the short-lived 32P isotope for
investigations o f organophosphorous compounds, which illustrated that differing metabolic pathways predominated in various organisms, resulting in different active materials predominating.
Use o f neutron activation o f elements was an interesting development that could prove o f use in improving pesticide efficiency. Improved application o f pesticides obviously eliminates the risk o f unwanted biological effects by diminishing the environmental burden o f xenobiotic compounds, and examples o f achieving control with controlled release formulations were described, using much diminished amounts o f pesticides.
Studies o f the environmental behaviour of elements using isotopes were not overlooked. The example o f nitrogen using stable isotopes clearly showed the interrelation between soil, crop, air and water and recirculation among the components and organisms.
Heavy metals are used as fungicides and tend to accumulate in land and, even more, may accumulate from fertilizing land with sewage sludge contaminated with industrial wastes. As such, there is concern about the transfer o f heavy metals to crops for human consumption. Here, studies with radioisotopes and nuclear activation provide some reassuring evidence about uptake from contaminated soils and distribution in cereals.
CONSULTANTS' MEETING ON PERSISTENT PESTICIDES
A N D HERBICIDES IN THE TROPICS
USING ISOTOPE TECHNIQUES
INTRODUCTIONA group o f consultants met in R o m e during the Symposium to assist the Joint F A O / I A E A Division in determining whether or not programmes involving persistent pesticides and herbicides in the tropics should be developed by the Joint Division and, if so, what specific types o f programmes should be considered.
Since there was a natural division o f subject matter, the consultants' group considered each separately. There was little difficulty at arriving at consensus regarding the advisability o f initiating programmes on the use o f herbicides in the tropics. However, in the case o f persistent pesticides, such as DDT, dieldrin, lindane, BHC, there was considerable discussion regarding the advisability o f such a programme. Scientists and administrators familiar with pesticide regulations in developed countries are well aware that persistent pesticides, such as DDT and dieldrin, have either been banned or their use patterns greatly reduced because o f environmental or human health concerns. The primary point o f discussion was whether or not there was sufficient evidence available to indicate that the fate, including metabolism, degradation, residues, etc., was sufficiently different under tropical conditions than that under temperate conditions to warrant initiation o f a study o f persistent pesticides under tropical conditions. It is known, for example, that the more intensive UV light in the tropics degrades pesticides more rapidly and that the increased rainfall and higher ambient temperatures also influence degradation o f pesticides.
The following is a brief summary o f the consultants' report.
PERSISTENT PESTICIDES IN THE TROPICSInformation in scientific literature suggests that organochlorines and other persistent pesticides are degraded much more rapidly under tropical or subtropical than under temperate climatic conditions, but more data are needed from experiments deliberately designed to explore this phenomenon. A reappraisal o f the properties o f persistent pesticides should be conducted under conditions closely proximating their use in tropical and sub-tropical climates;
in other words, using open-air techniques that can provide data comparable as far as is possible with data obtained by similar techniques in temperate climates.
The specific sequence o f events recommended by the consultants is
(1) A literature search should be conducted for publications on organochlorines, etc., relevant to their fate and behaviour in temperate and tropical/subtropical climates.