PESTICIDE RESIDUES IN THE ATMOSPHERE

PART IV. OCCURRENCE AND DISTRIBUTION OF PESTICIDE R E S ~ U E S

PESTICIDE RESIDUES IN THE ATMOSPHERE

Z. Jegier Research Institute of Zndustrial Hygiene & Air Pollution, School of Hygiene

Universite de MontrCal, Quebec, Canada.

Considerable attention is now being devoted to the new factors in man's ecology that first became apparent when the widespread use of pesticides led to a measurable pollution of his environment. This review considers, as succinctly as possible, the present state of the art of measuring pesticide pollution and presents some conclusions based on these measurements.

Since pesticides are present in hundreds of millions of acres of arable land, it is possible that a sizable proportion of the residues from these pesticides is volatiliz- ing into the atmosphere. Harris and Lichtenstein,' for example, demonstrated in 1961 that volatilization is a major factor in the disappearance of aldrin, dieldrin, heptachlor, and y-benzene hexachloride from soils treated with these pesticides. Pesticides can also enter the atmosphere by direct drift from dusting or spraying operations, from the effluents and vapors of industrial processes, and from the use of household aerosol sprays, thermal sprays, and the like. These drifting pesticides may then be washed out of the atmosphere to some extent by rain, or they may leave the air directly by sorption on soil.

Whatever the manner of the entry of pesticide residues into the atmosphere, recent studies indicate that today they may be present in the atmosphere in any part of the world. It has become clear that pesticide residues are being continuously redistributed, and that these residues are sometimes redeposited far from the original sites of application. Contemporary man must face the fact that every meal he eats contains some quantity of pesticide residue, however minimal, and he may soon face the possibility that every breath he draws will also contain some trace of pesticide, however minute.

DEGREES OF EXPOSURE

If we assume that pesticide residues in a nation's food supplies can be monitored and ~ o n t r o l l e d , ~ , ~ then obviously we must investigate the quantities and effects of these residues in the atmosphere. The amount that can be absorbed depends primarily on what concentrations are present in the air,5 and this provides us with three general levels of population exposure in a complex society. The population group exposed to the highest concentrations is, of course, that composed of those whose occupations keep them in environments, the air of which can be assumed to be highly contaminated: for example, workers in pesticide-manufacturing or formulating plants, operators of pesticide sprays, and users of household aerosol pesticide sprays6 Populations living in rural or urban communities near areas where agricultural pesticides are in use, or where insect-control operations are under way, compose the next group,7 but they are exposed to much lower concentrations. Finally, the general population, living far from sites of pesticide usage, is exposed to a minimum concentration. It is the level of this minimum concentration of pesticide residues in the general atmosphere that attracts the bulk of scientific and informed public concern today.

143

144 Annals New York Academy of Sciences

HIGH EXPO SURF.^: A FIELD STUDY

Consideration of some actual concentrations to which a segment of the most exposed group has been subjected over a period of time and of the effects this exposure has had on individual health mav help to provide a certain perspective when evaluating data on pesticide pollution of the general atmosphere.

From 1962 through 1964 the University of MontrealR carried out a field study on the possible health hazards of pesticide use. Although some of this work was carried out within the City of Montreal, the major portion of the study was concentrated on the agricultural region south of the city. This region is composed of many small family-owned apple orchards, vegetable farms, and greenhouse operations and includes a representative proportion of other pesticide users such as cattle ranchers, pest exterminators, and owners of public eating places. Al- though ample data are available on the amount of pesticides in the air during spraying operations, the Quebec study sought to obtain information that would be unique in terms of extent and that would be obtained under circumstances of significant exposure of subjects.

Spraying in that region is usually carried out by the farmers and their sons; consequently, many of the same individuals are seasonally exposed over a period of years to what have been termed “highest concentrations.” No official poisoning data relative to pesticides are available from this region because the workers involved are self-employed and d o not come under the provisions of the Work- men’s Compensation Act of Canada that oblige injured or ailing workers to visit a physician for examinations, which are summarized in official reports. Another point of interest in this study is the level of pesticides in the air during spraying. The farmers involved generally use air-blast equipment in their apple orchards and high-pressure, or hand-operated, sprayers in vegetable fields. The insecticides used are almost invariable chosen and mixed by the farmer himself.

As a result of these practices, i t was found that about half of all owners of apple orchards in the region use concentrations much higher than those recom- mended per acre or per 100 gallons of water.g

Throughout the study, the concentrations of various insecticides in the air near the spray operators were determined, and respiratory and dermal exposures were measured. The analyses employed colorimetric methods and electron-capture chromatography. Concentrations of insecticides were determined by bubbling the air through alcohol in fritted-glass impinger-type equipment. The results are tabulated in TABLE 1. The list of insecticides given represents those most popular in this region at the time of the field study. Methoxychlor, lower in cost than pyrethrin, was widely used as a cattle spray, systox was commonly used in greenhouses, and chlordane was favored by pest exterminators. The concentrations used are similar t o those encountered in other studies, particularly studies from the United States. For example, the concentrations of parathion are very similar to those in findings reported by the American Cyanamid Company.I” The last insecticide on the list-lindane-was present in restaurant and coffee house environments in this region in concentrations of 0.1 mg/m3, and came from com- mercial thermal vaporizers used indoors for control of flies and other insects.

What significance does the presence of insecticides in the air have for those who must breathe that air? Using the respiratory and dermal exposure indices suggested by Durham and Wolfe,’l the so-called Percent Toxic Dose ( P T D ) can be calculated, and this serves as an indication of the degree of poisoning. How- ever, it is impossible a t present to interpret fully the relationship between the P T D figures derived from the Quebec study and the symptoms found in, or the

Jegier : Pesticide Residues in the Atmosphere TABLE 1

145

CONCENTRATIONS OF INSECTICIDES IN THE AIR DURING SPRAYING AT VARIOUS LOCATIONS IN QUEBEC, CANADA AND IN THE UNITED STATES (mg/m")

Number Concentrations in Air Samples Range Mean

Insecticides of -~ Areas of Most Frequent Use

Malathion 4 0.41- 0.76 0.59 apple orchards, vegetable fields Sevin 7 0.18- 0.81 0.60 apple orchards Endrin 3 0.00- 0.00 0.00 potatoe fields Endrin* 3 0.02- 0.09 0.05 vegetable fields Parathion 10 0.05- 0.26 0.15 appleorchards Guthion 20 0.05- 2.55 0.67 appleorchards Guthion** 5 0.26- 6.20 2.77 Chlordane 8 0.8 - 0.92 0.44 apartments, stores, cafeterias Diazinon 6 0.26-10.20 2.68 cloakrooms Methoxychlor 10 0.50- 4.50 7.68 barn interiors, cattle spraying Systox 5 4.22-19.60 9.15 greenhouses Lindane

Parathion 0.00- 0.06 0.03 orchards (Batchelor, Walker) (vaporization) 20 0.04- 0.78 0.10 restaurants, stores, hospitals, etc.

0.00- 2.43 0.53 tank filling 0.13 orchards (American Cyanamid

0.36 orchards (Stearns e ta! . ) Co. report)

* During spraying by aircraft. *' During tank-filling operations.

complaints expressed to survey teams by, the subjects. It can be said only that some degree of poisoning did occur among the subjects. The calculated PCD data are tabulated in TABLE 2. These are maximum percentages, calculated from maximum respiratory and dermal exposures.

To obtain a clearer picture of the effect of insecticides in air on spray operators and their families under the circumstances already described for this region, the University of Montreal initiated a special field survey in 1964, with the intention of continuing it each summer. During and immediately after spraying season, medical students from the university, equipped with elaborate questionnaires, gather data on symptoms and complaints expressed by apple growers and their

TABLE 2

EXPOSURE VALUES OF SPRAY OPERATORS I N QUEBEC, CANADA TO INSECTICIDES CALCULATED AS PERCENT TOXIC DOSE

-.

Insecticide

Malathion Diazinon Methoxychlor Chlordane Sevin Endrin Parathion Guthion svstox

Percent Toxic Dose

0.002 0.022 0.003 0.009 0.02s 0.29 0.43 0.72 1.43

Dermal exp. (mg/hr) + Resp. exp. (rng/hr) X 10

Dermal LD, (mg/kg) x 70 Percent toxic dose = - x 100


families following exposure to insecticides in the air. The subjects are also asked about the measures they take in the event of poisoning. Such surveys were carried out in 1964, 1965, and 1966 in communities within the original field study region as a supplement to that study. Some of the results are summarized in TABLES 3 and 4.

About 30 per cent of the people interviewed complained of some illness or

TABLE 3 APPLE GROWERS AND MEMBERS OF THEIR FAMILIES COMPLAINING OF POISONING SYMPTOMS DURING THE 1NSECTlClDES SPRAYING SEASON AT VARIOUS COMMUNlTlES IN QUEBEC, CANADA

Number of Subjects Interviewed Complaining Percentage

Community Complaining

Rougemont St-Joseph-du-Lac Franklin Center St-Paul d’Abbotsford St-R6mi St-Hilaire Hemmingford Chateauguay Laval est Laval ouest Sherrington Ste-Clothilde St-Amable

5 04 236

95 284 21

136 104 192 43 12 14 10 4

161 115 42 39 11 44 20 51 15 9 5

2 -

32 49 44 14 41 32 19 30 35 15 36

50 -

Total 1661 520 31 1 TABLE 4

POISONING SYMPTOMS OF APPLE GROWERS AND MEMBERS OF THEIR FAMILIES AFTER EXPOSURE TO INSECTICIDES DURING THE SPRAYING SEASON IN QUEBEC, CANADA

Symptoms

Irritation of eyes Headache Dermatitis Nausea Weakness Dizziness Abdominal cramps Rhinitis Adenitis Fatigue Numbness Chest pains Insomnia Loss of appetite Vomiting Diarrhea Thirst Eyes watering Smarting sensations Nasal catarrh Nervousness

Subjects Complaining Number Percentage

113 54 40 45 21 39 22 4 2

56 18 11 9

20 11 6 2 9 I

14

23 11 6 9 4 8 4 0.8 0.4

11 4 2 2 4 2 1 0.4 2 1 3

20 4

Duration (days)

2 1 I 2 3 1 1 3 hospital 1 1 2 1 1 4 3 6 hours 2 1 2 2

Jegier : Pesticide Residues in the Atmosphere 147

discomfort, as shown in TABLE 3. No significant variation in the relative occurrence of individual complaints or symptoms was found when these communities were compared.

The list of complaints or symptoms investigated by the student teams is shown in TABLE 4. The most frequent complaints were eye irritation, fatigue, and headache. It will be noted that the complaints tabulated here closely resemble the symptoms of poisoning by organophosphorcs insecticides. The duration of illness or distress is generally short. usually a matter of days only, as indicated in TABLE 4. The subjects concerned generally do not consult a doctor: they follow the old- fashioned regimen of drinking large amounts of milk and getting adequate bed rest.

INTERMEDIATE EXPOSURES

Although the Quebec field 5tudy concentrated on the health hazards to spray operators and their families, some attention was given to the second general level of exposure alluded to earlier, that involving those living close enough to the sprayed areas to receive insecticide residues in the air through drift or vaporization. In this context, it is significant that Yates and Akesson'z in 1963 reported that tracers used in air pollution studies had been identified as far as 22 miles from the areas of original application. Although the concentrations involved are usually small, the possibility remains that more people may have been affected by drifting pesticide residues than the surveys showed, particularly when the time periods involved are considered. The type of outbreak that could occur has recently been reported from the State of Washington by Quinby and Doornink.I3 On two related occa- sions, some tetraethyl pyrophosphate (TEPP), which was being applied to hop vineyards by airplane in accordance with practices established over a 16-year- period, drifted over nearby farming communities and caused small outbreaks of mild topical pulmonary poisoning.

During the Quebec study, it was observed that, while apple orchards in the community of Rougemont were being sprayed with organophosphorus insecticides from air-blast equipment, there was evidence of these compounds in the air in residential areas located between 1,000 to 2,000 feet from the orchards. Measurable quantities of Guthion@, Sevins, malathion, and parathion, a popular insecticide in Quebec at that time, were found in concentrations of up to 0.5 mg/ m3.

In the United States, TaborI4 has demonstrated that the air over both urban and rural communities contains pesticide residues that directly reflect pesticide applications in local agricultural and insect control operations. In his study, airborne pesticides were collected by standard high-volume samplers positioned near the centers of six small towns surrounded by farming activities. Spraying occurred at random with respect to the sampling periods. Areas of spray application were generally at least a mile from the sampler. Sampling was also carried out in a scattered rural community a few miles distant from areas of pesticide applications. To round out this study, sampling was done in two small-to-medium communities and in one large city to determine the possible air-pollution effects of local pest- control programs.

Analyses of the deposits on the glass fiber filters were carried out with an electron-capture detector and a sodium-thermionic detector. Both disclosed measurable quantities of dichloro-diphenyl-trichloroethane (DDT) and chlordan in the atmospheres of the agricultural towns, and DDT and malathion in the atmospheres of the communities close to the pest-control operations. Results of


Tabor’s study are shown in condensed form in TABLE 5. It will be noted that the concentrations of DDT in the air ranged from below detectable levels to 23 ng/m:l for the agricultural towns and from below detectable levels to as high as 8,000 ng/ni3 for the communities near insect-control applications. Tabor considers these as minimum values only, since n o satisfactory method for collecting pesticide vapors was readily available, and particulate residues collected were prob- ably reduced by vaporization during sampling. This loss factor has been discussed by Rondia’s in a report on the collection of polynuclear hydrocarbons.

TABLE 5 CONCENTRATIONS OF INSECTICIDES IN THE AIR OF AGRICULTURAL COMMUNITIES

IN THE UNITED STATES (NG/M3)* .- ~-

Community No. of Samples DDT Chlordane Malathion Analyzed

Florida City, Fla. 20 0.1-7.6 n.d. - Lake Alfred, Fla. 16 0.1-1.3 0.6-1.9 - Fort Valley, Ga. 14 0.3-9.9 0.4-6.0 -

Inman, S . C. 18 0.1-2.2 0.2-5.6 - Leland, Miss. 15 0.4-22 0.3-2.2 - Newellton, La. 10 0.5-7.7 0.3-2.6 - Lake Apopka, Fla. 11 0.3-8500 1-31 - Community A 4 - - 8-22 Community B 6 100-8000 - 1-30

- 10 0.4-4.0 n.d.

Community C 3 100-430 - 6-140 -

* Source: TABOR, E. C. 1966. Contamination of urban air through the use of insecticides. Trans. N. Y . Acad. Sci. 2 8 ( 5 ) : 569-578,

RESIDUES IN THE GENERAL ATMOSPHERE

The possibility of some hazard to the health of that large segment of the population exposed to minimum concentrations of pesticide residues in the air, the concentration corresponding to their distance from agricultural operations, has become the concern of public health officials. This possibility is also linked in their minds, the author believes, with the problem of the existence of carcinogenic polynuclear hydrocarbons in the a t m ~ s p h e r e . ~ Current research findings indicate that the general atmosphere of the globe may well be polluted by pesticide residues, the extent of pollution depending o n the location and meteorological conditions of a given community.

The presence of insecticide residues in the general atmosphere has been proven from analysis of rain and air samples by several researchers in the United States and England. In 1965, Wheatley and Hardman,lG working in agricultural sur- roundings in central England, reported the presence of organochlorine insecticides in rainwater samples. Each sample was collected over a period of one calendar month in a glass container inside an eight-inch diameter copper rain gauge placed on short grass. Supplementary samples were collected in chemically clean glass dishes placed about 40 c m above the ground in the center of a grass field, and these samples were emptied into glass bottles for the laboratory in each case as soon ar it stopped raining. To quote the team’s own report: “Throughout the work scrupulous attention was given to minimizing potential contamination or interference from reagents or other within-laboratory sources. The all-glass apparatus used was washed successively in hot water with detergent, distilled water,

Jegier : Pesticide Residues in the Atmosphere

y-BHC -

Mean Samples Range

Month-long samples April-Oct., 1964 77-120 91 Nov. 1964-Feb., 1965 32-164 100

___~ ~~~ ~~ . ~

Supplementary sunrples January & March, 1965 12-52 29.1 ~ - - - ~~ ~~~~~ ~

149

Dieldrin ~

Range ____~___

19-36 10-25

~~~~~~

3-16 2-4 ~ . _ _ _ _ . _

acetone and hexane. and then heated for several hours at 100-1 10” C. It was rinsed again with acetone and hexane prior to use and the purity of the final rins- ings was tested by gas/liquid chromatography. Reagent blanks were also proc- essed concurrently with the samples.” The analytical method employed hexane extraction and separation by thin-layer chromatography, with final determinations carried out by electron-capture chromatography. The same degree of thorough- ness and care appears to have been applied to analysis and determination: the results are shown in TABLE 6.

The highest average concentration of pesticide residue found was in the period November through February and this was 100 ppm-m of y-benzene hexachloride (7-BHC). Wheatley and Hardman concluded that the presence of the organochlorine insecticides in English rainwater can be attributed to vaporization of pesticide residues from thin-surface layers of soils that had been treated with aldrin, dieldrin, y-BHC, and DDT. In addition, there are intermittent and variable direct contributions from local and possible global pesticide applications. They concluded: “In view of the worldwide use of organochlorine insecticides and the extensive distribution of their residues in soil, together with the foregoing evidence [the rainwater study], it is possible that they might now contaminate the atmosphere continuously.”

Another study, carried out in England bv Abbott and his colleague^,^^ has also demonstrated the presence of organochlorine insecticide residues in the general atmosphere. For this, month-long samplings of rainwater were collected at two stations in central London in all-glass equipment that had amber-colored receiving vessels to retard photochemical degradation. Analyses of these samples were made by thin-layer and electron-capture chromatography. The limits of detection by this method were 5 ppm-m for the isomers of BHC and 10 ppm-ni for the other organochlorine pesticides in general use in the United Kingdom. This research team confirmed the presence of a-, p-, and y-BHC, dieldrin, DDT, tetrachloro- diphenyl-ethane ( T D E ) , and dichloro-diphenyl-ethane ( D D E ) . The findings are tabulated in TABLE 7, from which it can be seen that dieldrin concentrations reached as high as 95 ppm-m, and those of DDT as high as 400 ppm-m. Rainfall is not shown in TABLE 7 for the Cornwall House station, but it is of interest to

Reagent blanks 1-3 2 1-4 3 - <0.5


note that it was located 1.45 k m distant from the State House station for which rainfall is given.

Abbott and his co-workers suggest: “The atmosphere carries, either as vapor or by occlusion on dust particles, small amounts of the organochlorine pedc ides in common use in the United Kingdom and [these] are ‘scrubbed out’ by rain and snow.”

In the United States, Cohen and his co-workersl* reported in 1964 on the presence of pesticide residues in rainwater. Their findings showed an organic chlorine content of 0.3 ppb, along with atrazine and 2,4-dichlorophenoxyacetic (2,4-D) ester at levels of approximately 0.1 ppb each.

In an additional study reported in part by Weibel and his colleagues1g in 1966, 90 samples of rainwater were collected in three areas of Ohio and analyzed by microcoulometric gas chromatography. All 9 0 samples showed the presence of organic chlorine in concentrations ranging from 0.02 to I . 18 ppb. In a later report, Cohen Pinkerton’O elaborated on the methods and conclusions of this study. TABLE 8 shows the concentrations found for DDT, DDE, and BHC in the Ohio study. Chlordan, heptachlor epoxide, aldrin, dieldrin, and the isooctyl ester of 2,4,5-trichlorophenoxyacetic (2,4,5-T) were also reported.

Cohen and PinkertonZ0 have also reported recently on evidence they obtained for the long-distance transportation of pesticides through the atmosphere. In Cincinnati, Ohio, an analysis of dust from a storm that originated in the New Mexico-Texas region about 30 hours previously showed the presence of DDT, DDE, 2,4,5-T, ronnel, heptachlor epoxide, chlordan, and dieldrin, as well as indications of other pesticides. These researchers comment: “It is reasonably certain that soil is constantly being picked up by winds, transported at high altitudes over long distances, and deposited elsewhere either by simple sedimen- tation or by rain. While the data [from this study] would incriminate dust as the distributor of pesticides, it is entirely possible that they may also enter the atmosphere simply by volatilization.”

The presence of pesticides in the general atmosphere has also been confirmed

TABLE 7

IN LONDON, ENGLAND (PPM-M)* ORGANOCHLORINE PESTICIDE RESIDUE LEVELS IN RAINWATER

Month 1965

Rain (mm)

a- BHC

4- BHC B&C

HEOD (dieldrin)

P.P’ DDE

P.P’ TDE

PPP’ DDT

Station - Cornwall House, London, S.E. I, England.

Feb. - 40 90 90 50 70 - 400 Mar. - 15 - 60 60 20 - 115 Apr. - 30 - 80 50 - 300

- 20 65 70 95 - 190 - 30 - 55 25 - 15 70 June

July - 25 - 40 10 15 85 85

- - May

Station - State House, High Holborn, London, W.C. I, England.

Mar. 33.4 10 - 20 20 Apr. 37.3 20 - 70 70 - 100 140

220 36.6 20 25 55 50 June 36.2 20 __ 155 20 - 50 125 May

July 78.0 30 - 70 15 10 20 80

.. __ - - - - -

- ___-- * Source: Abbott, DTC., R. B. Harrison, I . O G . Tatton & J. Thompson. 1965. Nature 208:

1317.


Compound Range

Organic Chlorine Max. Min. Mean

DDT Max. Min. Mean

DDE Max. Min. Mean

BHC Max. Min. Mean

. -. .

~~~

. .. ~ ~

_ _ ~ _ ~ ~~ ~

151

- ____ Concentrations .-____ Ripley Coshocton Cincinnati

0.69 0.32 1.18 0.10 0.02 0.09 0.30 (36)** 0.20 (15) 0.21 (34)

__ ~

~_ ~

0.29 0.12 1.30 0.02 0.02 0.07 0.15 (23) 0.07 (3 ) 0.34 ( 8 )

0.05 - 0.02 0.01 - 0.005 0.03 (13) 0.00s (1 ) 0.02 (7)

~ ~ ~ _ _ _ _ ~. ~ ~~~~

-~ ~~ ~ ~-

0.07 - 0.07 0.01 - 0.01 0.05 (23) 0.006 (1) 0.02 (10) _ _ _ ~

by analyses of air samples. In 1965. for instance, Abbott and his colleaguesz1 in England collected air samples in central London, using suction at the rate of about 15 I/min through 100 ml of dimethylformamide in apparatus that provided adequate diffusion. The samples were analyzed by hexane extraction and determined by thin-layer and electron-capture chromatography using two different columns. These researchers emphasize: “The concentrations of these residues are so low that it is necessary to work almost at the limit of sensitivity of the detection systems at present in use. For this reason, scrupulous care is necessary in order to avoid contamination at each manipulative stage, from the initial apparatus preparation to the final injection on to the gas chromatograph. Blank experiments must be performed at each stage and on all materials used. Particular care is required to exclude laboratory dust, for i t is found that it is frequently a carrier of interfering electron-capturing materials.”

TABLE 9 shows the pesticides identified from this examination of the 8000 1 of

TABLE 9 ORGANOCHLORINE PESTICIDES FOUND IN AIR, IN LONDON, ENGLAND (PPM-M) *

Station - Cornwall House, London S.E. 1, England.

Concentrations Found by Gas-liquid

Silicone E.301 Apiezon L’

Rr Range of Chromatography on Compound Chromatoplate Area

m-BHC 0.37-0.48 1 1 .. _.._

y-BHC 0.27-0.36 5 11 Dieldrin (HEOD) 0.17-0.26 18 21 p, p’-DDE 0.75-0.84 4 7 p,p’-DDT 0.54-0.64 3 3 p, p’-TDE 0.37-0.48 3 3

* Source: Abbott, D. C., R. B. Harrison, J. O’G. Tatton & J. Thomson. 1966. Nature 211: 259.


London air sampled in the study. The presence of a- and 7-BHC, dieldrin, p,p’- DDE, p,p’-TDE, and p,p’-DDT was confirmed, as shown. The highest concentration found was that of dieldrin: 18 and 21 ppb, depending on which column was used.

Abbott and his colleagues observed: “Although the concentration of [residues] in air is lower by a factor in the range of 10-1 00 than that in rainwater, the vastly greater volumes of air may render this contribution of greater significance.” This statement suggests the desirability of sampling large volumes of air. In the United States, an automatic device for collecting air samples containing halogenated hydrocarbon and organophosphorous pesticide residues in vapor and particulate form has been described by J . W. Dust and vapors are trapped in the ethylene glycol, extracted with hexane, and analyzed by gas chromatography or by spectrophotometry. Sensitivities are in the order of fractional parts per billion, with the device running at a rate of 10 Vmin for one or two hours.

Studies carried out in the United States by the Department of Public Health, State of C a l i f ~ r n i a , ~ ~ showed the presence of DDT in air samples collected from four California cities in 1963. The concentrations range from less than 0.5 ng/m3 up to 19.0 ng/m3. Data from these studies are tabulated in TABLE 10, and were supplied by Dr. I rma West with the following precautionary note: “Care should be taken in interpreting these figures. The sampling program was, a t best, provi- sional and the period of the year representative of rather specialized meteorological and agricultural conditions. Evidence was obtained that DDT may be lost in some way from the filter paper. At any rate, it would be better not to look upon these results as measurements, but to consider them as evidence that measurable quantities of D D T can be found in the air of those cities.” A sampling study in the city of Pittsburgh, Pa. by Antommaria and his colleagues2* also indicates that D D T can be present in an urban atmosphere that is distant from any large-scale agricultural activity.

TABLE 10 CONCENTRATIONS OF DDT I N SAMPLES OF AIR COLLECTED IN BERKELEY, SACRAMENTO,

STOCKTON, AND FRESNO, CALIFORNIA BETWEEN OCTOBER 31 AND DECEMBER 5,1963 (NC/M3) *

Samole Location Date Recovery DDT Concentration in Air - ~~~

3858 Berkeley 10/3 1/63 12 pg 4

3866 Sacramento 11/12 4 2 3867 Sacramento 11/22 2 0.9 3868 Sacramento 11/26 4 2 3915 Sacramento 11/29 0 0 3916 Sacramento 12/ 5 0 0

3861 Stockton 11/18 <1

3919 Fresno 11 /13 5 2

3922 Fresno 11/26 6 3 3923 Fresno 11 /29 5 2

3948 Berkeley 12/ 5 9 1 3 (Spraying on Cedar St.)

<0.5 <0.5

3860 Stockton 11/14

3862 Stockton 11/26 2 0.9 3922 Fresno 11/12 46 19

3921 Fiesno 11/20 <1 <0.3

* Source: Bureau of Director of Sanitation, California State Dept. of Public Health.


CONCLUSIONS

Although this review i s merely a glance at the most significant findings of current research in the field, the presence of organochlorine pesticide residues in the general atmosphere can be accepted as proven. Their concentrations may not have been measured precisely or absolutely, but their existence is a fact. Although their quantities may presently be minimal compared with those absorbed from foodstuffs, they must nonetheless be added to the long list of undesirable air pollutants.

Development of standard sampling and analytical methods can be expected to follow in this field as public and scientific interest grows. Voluminous files of accurate data from all parts of the world will be added to those slim volumes now in the literature. However, one problem is likely to remain obscure and contro- versial for a long time to come: What is the biological significance of these minimum pesticide residues in the atmosphere? A clear-cut clinical judgment on the physiological effects of low concentrations of pesticides in air cannot be expected for many years. In the interval, we will be living with a situation that may turn Out to be injurious to health when all the evidence is in.

At this point, we can be certain only that some of these pollutants are harmful to health in large quantities, as, for example, in the case of dieldrin. We have scientific evidence to show that unusual weather conditions can convey pesticides in injurious concentrations to populous centers. However, at this stage we can only suggest that long-term exposure to pesticide residues in the general atmosphere may have cumulative effects on human health. Nevertheless, it is difficult to dismiss the thought that this will be the judgment of the future.

In the absence of hard data, the wisest long-range objective should involve some control over pollution of the atmosphere with pesticides. In the intervening period, public and legislative thinking must somehow be guided between the view on the one hand that pesticides are entirely harmful to man’s ecology and on the other that society must always pay for its material progress by accepting physical risk. Much of the responsibility for this kind of guidance rests with those now involved in the field of pollution research.

153

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PESTICIDE RESIDUES IN THE ATMOSPHERE