Reduction of lead concentrations in vegetables grown in Tarragona Province, Spain, as a consequence of reduction of lead in gasoline

~

Pergamon

Environment International, Vol. 21, No. 6, pp. 821-825, 1995 Copyright ©1995 Elsevier Science Ltd Printed in the USA. All rights reserved 0160-4120/95 $9.50+.00

0160-4120(95)00091-7

REDUCTION OF LEAD CONCENTRATIONS IN VEGETABLES GROWN IN TARRAGONA PROVINCE, SPAIN, AS A CONSEQUENCE OF REDUCTION OF LEAD IN GASOLINE Monserrat Belles, Angela Rico, Marta Schuhmacher, and Jos6 L. Domingo Laboratory of Toxicology and Biochemistry, School of Medicine, "Rovira i Virgili" University, 43201 Reus, Spain Jacinto Corbella Toxicology Unit, School of Medicine, University of Barcelona, 08036 Barcelona, Spain

E19503-172 (Received 7 March 1995; accepted 21 August 1995)

Lead concentrations were determined in 350 samples belonging to 13 different species of vegetables from Tarragona Province, Spain. The samples were subjectedto lead analyses by graphite furnace atomic absorption spectrophotometry.During the period 1989-1994, an average decrease for lead concentrations of 69% was estimated. Spinach showed the lowest reduction in lead content (6%), while the highest decreases were observed for onion (87%) and leek (90%). Taking into account the average consumption of vegetable foodstuffs by the population of Tarragona Province, the daily lead intake through edible vegetables was reduced from 41.5 p.g/d in 1989 to 10.6 Ixg/din 1994. The results of the current study demonstrate a substantial decline in the lead levels of vegetables from Tarragona Province. The major cause of this decline is most likely the reduced leaded gasoline consumption.

INTRODUCTION

gasoline either singly or as mixtures to achieve desired octane numbers (Ou et al. 1994). However, in recent years, efforts have been made in a number of countries to reduce the lead concentrations in gasoline and to replace lead by other compounds. The reduction and/or replacement of petrol lead is the likely contributor to the decline in blood lead levels observed in several recent surveys carried out in various countries (Brody et al. 1994; Grobler et al. 1992; Maresky and Grobler 1993; Pirkle et al. 1994; PSnkii et al. 1993). The contribution of aerosol lead to the intake of this metal has been estimated to be in general low, whereas it is also low compared with the tolerable intake levels of lead (Kim and Fergusson 1994). In contrast, lead from gasolines may contribute significantly to lead intake (Pirkle et al. 1994; Watanabe et al. 1994). In addition to drinking water and beverages, groups of foodstuffs, such as cereals, vegetables, and fruits, contribute most to the total intake of lead by adults. In turn, infants' lead intake

Lead is widely dispersed in the environment (Nriagu and Pacyna 1988) and, if it is absorbed by the human body, may produce hematological toxicity, neurotoxicity, and renal toxicity (Landrigan 1982). Although environmental lead pollution may proceed from many different sources, in countries and regions where leaded gasoline is used, atmospheric lead pollution from vehicular exhaust aerosols can be a major source of lead deposition on soil, water, sediments, and biological communities (Fergusson 1986; Harrison and Laxen 1981; Landrigan 1982; Romieu et al. 1992). For several decades, organic lead (tetraethyl lead and its analogous chemical tetramethyl lead) have been added to

Correspondence and reprint requests to: Dr. Jos6 L. Domingo, Laboratory of Toxicology and Biochemistry, School of Medicine, URV, San Lorenzo 21, 43201 Reus, Spain. 821

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can be strongly influenced by the lead content of water and by storage of infant formulas in lead-soldered cans (Galal-Gorchev 1993). However, the contribution of foods to the lead intake depends obviously on the quantity of food consumed in each region or country, as well as the lead concentration in the food (Carrington and Bolger 1992; Galal-Gorchev 1993; Schuhmacher et al. 1991; Watanabe et al. 1994). Information provided by 25 countries (1980-1988) showed that lead intake ranged from 1 to 9 ~tg/kg.d (or 63 ~tg/kg.week) approaching or exceeding the Provisional Tolerable Weekly Intake (PTWI) of 25 ~tg/kg in four countries providing data (Galal-Gorchev 1993). On the other hand, a Provisional Tolerable Total Dietary Intake of 6 ~tg/d was suggested for protection of young children from the toxic effects of lead (Carrington and Bolger 1992). Among the different food groups that can contribute to the ingestion of lead through diet, vegetables are of special concern. Metals in plant tissues may have two different principle origins: absorption from soil, and deposition from the atmosphere (Bosque et al. 1990; Nwosu et al. 1995; Salim et al. 1993; Zurera et al. 1987). Previous studies on the levels of lead in edible vegetables showed that the aerial plants zones were the most important entry point for lead (Bosque et al. 1990; Havre and Underdal 1976; Zurera et al. 1987). Consequently, the uptake of lead by plants from soil and from the atmosphere is considered as a serious human health problem (Davies and White 1981; Kim and Fergusson 1994; Landrigan 1982; Pirkle et al. 1994). In recent years, the levels of lead in Spanish gasoline were reduced from 0.4 g/L to 0.15 g/L, while the number of vehicles consuming unleaded gasoline has also been markedly increased. The decrease in the concentrations of lead in fuel, as well as the increase in the consumption of unleaded gasoline should lead to a consequent reduction in airborne levels of this metal. Recent studies have shown that the limitation in the use of lead in gasoline induced a resulting decrease in the atmospheric lead concentrations (Boutron et al. 1991; Lee et al. 1994; Migon et al. 1993,1994; P6nka et al. 1993; Simmons and Knap 1993). In turn, this decrease would be the major contributor to the observed decline in the blood lead levels of the general population (Brody et al. 1994; Grobler et al. 1992; Maresky and Grobler 1993; Pirkle et al. 1994; P6nk/i et al. 1993). It is well established that lead from gasoline contributes to the content of lead in food (Landrigan 1982; Pirkle et al. 1994). However, because gasoline lead enters food through multiple pathways, it is difficult to make a quantitative estimate of the reduction in food lead that would result from decreasing lead in gasoline. During

M. Bell6set al.

1988-1989, samples of vegetables grown in Tarragona Province (Catalonia, NE Spain) were collected to determine the lead levels, as well as to establish the contribution of these vegetables to the total dietary lead intake (Bosque et al. 1990). The purpose of the present study was to reevaluate the lead content of vegetables from Tarragona Province according to the notorious reduction in the consumption of leaded gasoline. The decrease in dietary lead intake by the population of Tarragona Province was also determined. MATERIALS AND METHODS

Samples Edible vegetables were randomly obtained from commercial growers or from retail outlets during the seasons of 1994 when they were most abundant. The sources of the various vegetables were several locations in Tarragona Province, which was divided for the study in two areas (northern and southern), presumably exposed to different degrees of environmental pollution. A more extensive description of both areas was given in previous reports (Bosque et al. 1990; Schuhmacher et al. 1991). A total of 350 samples belonging to 13 different species was analyzed: carrot (Daucus carota), radish root (Raphanus sativus), onion (Allium cepa), leek (Allium ampeloprasum), garlic (Allium sativum), parsley (Petroselinum cripsum), chard (Beta vulgaris), spinach (Spinacia oleracea), lettuce (Lactuca sativa), leaves of celery (Apium graveolens), cauliflower (Brassica oleracea), cabbage (Brassica oleracea), and artichoke (Cynara scolymus). The vegetables were divided into the following four groups: roots and tubercles (carrot and radish root), bulbs (onion, leek and garlic), leaves and soft stalks (parsley, chard, spinach, lettuce and celery), and other garden produce (caulifower, cabbage and artichoke).

Chemical analysis Samples of vegetables were taken in plastic bags. Nonedible parts were removed according to household practices. Edible parts were then cleaned thoroughly with deionized water and placed on filter paper to eliminate excess moisture. When dry, 1 g of each sample was digested in a teflon bomb with 2 mL of 65% nitric acid (Suprapur, Merck, Darmstadt, Germany) heated at 110 °C for 18 h. After that, the volume was made up to 10 mL with deionized water and samples were analyzed. The analytical method used was the atomic absorption spectrometry using a Varian spectrophotometer equipped with a Zeeman corrector and a graphite furnace (Spectra A-30). The standard addition method was employed and NH4H2PO4 was used as matrix modifier. Three batches of

Lead reduction in vegetables by lead reduction in gasoline

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Table 1. Total lead content (lag/g wet weight) in vegetables from Tarragona Province, Spain: Comparisonbetween the results of the 1989 studya and those obtained in the current studyb. Species

1989 Study

Current study

Percentage of decrease (1989-1994)

Carrot

0.099±0.086

0.029+0.012

71

Radish root

0.101±0.091

0.027+0.020

73

Onion

0.167+0.125

0.017+0.022

87

Leek

0.356+0.250

0.052+0.048

90

Garlic

0.139+0.136

0.018+0.010

87

Parsley

0.320+0.142

0.131+0.072

59

Chard

0.194+0.175

0.147+0.139

14

Spinach

0.123+0.082

0.116+0.082

6

Lettuce

0.294+0.218

0.074+0.058

75

Celery

0.364+0.139

0.102+0.080

72

Cauliflower

0.154+0.194

0.029+0.021

81

Cabbage

0.143+0.118

0.042+0.037

71

Artichoke

0.097+0.089

0.062+0.072

36

"From Bosque et al. (1990). bValues are arithmetic means + SD. each sample were analyzed. Lead recovery was assessed by analyses o f Bovine Liver (National Bureau o f Standards SRM 1577). The mean recovery rate was 96.6%. Statistics

Differences between lead concentrations in edible vegetables from the northern and southern areas were analyzed by one-way analysis o f variance (ANOVA). Statistical significance was evaluated by the KruskalWallis test or the Mann-Whitney U-test. A probability o f 0.05 or less was considered significant. RESULTS AND DISCUSSION

Table 1 summarizes the lead concentrations o f all samples analyzed in the current study. The lead concentrations obtained in the 1989 study are also shown (Bosque et al. 1990). According to these data, it seems quite evident that the present levels o f lead are lower than those found previously. On average, the concentrations o f lead in edible vegetables grown in Tarragona Province were reduced from 0.177 ktg/g to 0.055 ~tg/g (a 69% decrease). Chard, parsley, celery, and spinach, which are species belonging to the group o f leaves and soft stalks, showed the highest lead levels, whereas the same species also

showed the lowest decrease (average 38%) in the lead content during the last five years. With the exception of celery, the remaining species did not present significant differences between the samples collected in the northern area and those obtained in the southern area o f Tarragona Province (Table 2). In the industrial area (northern area), the mean lead concentrations decreased from 0.194 ~tg/g (1989) to 0.063 ~tg/g (1994), with a percentage o f reduction o f 68%, whereas in the rural area (southern area), the lead levels diminished from 0.160 ~tg/g (1989) to 0.047 p.g/g (1994), with a 71% decrease. The differences in the percentages of lead reduction are probably be due to the fact that the lead emissions produced in industrial areas throughout the years might have provoked a saturation o f lead in soils. This saturation would now make a short-dated removal o f lead more difficult. The lead concentrations in vegetables from Tarragona Province, classified according to the four groups described in Materials and Methods are shown in Fig. 1. The lowest lead content corresponded for both studies to roots and tubercles (0.100 pg/g in 1989, and 0.028 ~tg/g in 1994), with a 72% decrease, whereas the highest percentage o f decrease in lead content was observed in the group o f bulbs: 87%. In contrast, the highest lead levels were found in the group o f leaves and soft stalks (0.257 ~tg/g in 1989, and 0.121 ~tg/g in 1994), with a 53% decrease.

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M. Bell6s et al.

Table 2. Lead concentrations 0tg/g wet weight) in vegetables from Tarragona Province according to the collection area: Comparison between the results of the 1989 study a and those obtained in the current study b.

Species

1989

PC

Northem area

Southern area

Carrot

0.081+0.079

0.118+0.096

Radish root

0.080±0.082

Onion

1994

tx

Northern area

Southern area

NS

0.030+0.011

0.029±0.016

NS

0.122±0.099

NS

0.029±0.020

0.024±0.022

NS

0.191±0.148

0.143±0.091

NS

0.017±0.022

0.019±0.010

NS

Leek

0.581±0.725

0.132±0.222

0.05

0.055±0.056

0.041±0.021

NS

Garlic

0.136±0.137

0.142±0.136

NS

0.022±0.010

0.006±0.001

NS

Parsley

0.333±0.133

0.305±0.158

NS

0.176±0.103

0.114±0.058

NS

Chard

0.328±0.163

0.061±0.070

0.01

0.187±0.125

0.134±0.156

NS

Spinach

0.144±0.060

0.088±0.136

NS

0.107±0.091

0.130~0.093

NS

Lettuce

0.357±0.463

0.231±0.141

NS

0.068+0.054

0.084+0.068

NS

Celery

0.392±0.279

0.336±0.080

NS

0.160±0.084

0.052±0.026

0.01

Cauliflower

0.059±0.066

0.250±0.233

0.05

0.038±0.024

0.014±0.006

NS

Cabbage

0.170±0.146

0.125+0.085

NS

0.065±0.060

0.030±0.013

NS

Artichoke

0.077±0.093

0.154±0.046

0.05

0.046±0.049

0.071±0.084

NS

aFrom Bosque et al. (1990). bValues are arithmetic means q- SD. CANOVA P value; NS, not statistically significant.

0,3

0,25

~,0,2 o

c0,15 o

i

"o

~ 0,1 0,05

Roots and tuberc.

Bulbs

Leaves and soft stalks Olher garden produce

1989 ~ 1994 Fig. I. Mean lead concentrations in vegetables from Tarragona Province according to the four established groups: Comparison between the results of the 1989 study and those obtained in the current study.

Lead reduction in vegetables by lead reduction in gasoline

O n the other hand, t a k i n g into a c c o u n t the a v e r a g e c o n s u m p t i o n o f v e g e t a b l e foodstuffs in T a r r a g o n a Prov i n c e , the d a i l y intake o f lead t h r o u g h v e g e t a b l e s b y the g e n e r a l p o p u l a t i o n o f that a r e a w a s 41.5 ~tg/d in 1989 (Bosque et al. 1990) vs. 10.6 ~tg/d in 1994. In a p r e v i o u s study, the authors found that the daily lead intake t h r o u g h diet for an a d u l t f r o m T a r r a g o n a P r o v i n c e w a s 115 ~tg/d ( S c h u h m a c h e r et al. 1991), w h i c h w o u l d signify that v e g e t a b l e s c o n t r i b u t e d with a 3 6 % o f the total d a i l y lead intake. A s s u m i n g that this p e r c e n t a g e m i g h t be the s a m e in 1994, it w o u l d m e a n a total l e a d intake o f 29 ~tg/d, w i t h a 7 4 % d e c r e a s e in the total d i e t a r y intake o f lead for the p e r i o d 1989-1994. A l o w e r d e c r e a s e ( 4 1 % ) in dietary intake o f lead w a s r e c e n t l y r e p o r t e d a m o n g the J a p a n e s e p o p u l a t i o n during the last decade, w h e n a t m o s p h e r i c lead concentrations were r e d u c e d from 13-140 n g / m 3 to 11-93 n g / m 3 ( W a t a n a b e et al. 1994). A c c o r d i n g to the results o f a n u m b e r o f studies s h o w i n g a significant d e c l i n e in b l o o d lead levels consistent w i t h the r e d u c t i o n o f l e a d in g a s o l i n e ( B r o d y et al. 1994; G r o b l e r et al. 1992; M a r e s k y and G r o b l e r 1993; Pirkle et al. 1994; P6nk~i et al. 1993), the c o n f i r m a t i o n o f a favora b l e i m p a c t o f the r e d u c e d d i e t a r y lead intake on the health o f the population o f T a r r a g o n a P r o v i n c e should be e v a l u a t e d in the n e a r future. This s u r v e y should assess w h e t h e r the effect o f r e d u c i n g lead e x p o s u r e from gasoline c o r r e s p o n d s with a m a r k e d decrease in the b l o o d lead levels o f the g e n e r a l population.

Acknowledgment--This study was supported by a grant from the Department of Environment, Generalitat of Catalonia. The authors thank the Servei d'Espectroscbpia, University of Barcelona, for excellent technical assistance.

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