Dioxin, Dioxin–Like PCBs and Indicator PCBs in Some Medicinal Plants Irrigated with Wastewater in Ismailia, Egypt

Abstract

Wastewater is often leaden with various contaminants that may accumulate in soils and can under some conditions enter the agricultural food chain. Concentrations of PCDD/Fs, DL-PCBs and NDL-PCBs have been determined using GC/HRMS in three of the commonly used medicinal plant (henna, rosemary, and moghat) grown on raw wastewater. In the case of henna and rosemary plants, all wastewater irrigated samples showed higher content of the studied contaminants than freshwater irrigated samples, while moghat samples, whether irrigated with freshwater or wastewater, had more or less the same content of the studied contaminants. Concentrations in plant samples ranged between 0.00004 and 0.865 pg WHO TEQ/g wet w for PCDDs, and between 0.03 and 1.86 pg WHO TEQ/g wet w for the PCDFs. Levels of PCB TEQ ranged from 0.005 to 0.76 pg/g wet w. In descending order, rosemary, henna, and moghat had the highest concentrations of total TEQ (PCDD/Fs + DL-PCBs). The congeners pattern in henna and rosemary samples was generally characterized by the dominance of PCDFs with a significant contribution from the lower (mono- to tri-) PCDFs. In moghat samples the profile was dominated by PCDDs, with OCDD contributing 100% to PCDDs. PCBs contribution to the total TEQ was on average 25%, 7% and 2% in rosemary, moghat and henna respectively. For NDL-PCBs, the sum concentration of 17 PCBs congeners increased from 2.65 to 4.13 ng/kg wet w in henna, and from 4.64 to 7.16 ng/ kg wet w in rosemary due to the irrigation with wastewater. Congener PCB 28 was the main contributor (60%) to sum 6 indicators in all samples, followed by PCB 52 (18%) and PCB 101 (6%).

Key Words:

• dioxins
• freshwater
• henna
• irrigation
• moghat
• PCBs
• rosemary
• wastewater

INTRODUCTION

Water shortage is becoming one of the most critical issues in a number of Middle East countries including Egypt. Growing demand caused by burgeoning population, industrial and agricultural development is posing a potential challenge to the limited supply of water, mainly provided by the Nile (about 98% of Egypt's fresh water). The use of wastewater is emerging as a potential alternative to augment the water supply in Egypt, especially in the agricultural sector that consumes almost 84% of Egypt's water budget (1). The use of wastewater in agriculture is providing an added value as it has special nutritional value supplementing growing crops. On the other hand, wastewater is often leaden with various contaminants that may render its use not environmentally sound. Polychlorinated dibenzo-dioxin/furan (PCDD/Fs) and dioxin–like polychlorinated biphenyls (DL-PCBs) are among the most sinister pollutants that end up in wastewater. These persistent environmental contaminants are potential carcinogens, with a strong tendency to bioaccumulate in various environmental segments. The main sources of PCDD/Fs and PCBs in urban wastewater are basically atmospheric deposition on soil and runoff (2) along with industrial emissions.

In Egypt, interest in the use of treated wastewater as a substitute for freshwater in irrigation has increased since 1980. Currently, 0.7 billion cubic meters per year (BCM/yr) of treated wastewater is being used in irrigation.

Up to now, there is no specific legislation regarding the maximum equivalent concentration levels of organochlorine compounds, especially PCDD/Fs and PCBs, in wastewater or sludge.

Generally the most common sources for dioxins emission in Egypt are solid waste and sludge burning. Open burning of domestic and some agricultural solid waste is a quite common practice. On the other hand some of the newly introduced industries such as pulp and paper bleaching and some metallurgic works would constitute another potential source of emission.

The mechanism of vegetation uptake of organic pollutants is governed by the chemical and physical properties of the pollutants, environmental conditions, and the plant species. For agricultural leaf crops the main source of contamination is direct organic contaminants, although some of them have high octanol/water coefficients that make it difficult for root uptake. However, vegetables grown in soil amended with sewage sludge increase PCDD/Fs concentration considerably (3).

Due to their low solubility in water and their lipophilic nature, these compounds are concentrated in the sewage sludge during wastewater treatment. Possible transfer pathways of these compounds into the human food chain would be food crops or grazing livestock that eat contaminated feed grown on sludge-amended soil or ingest contaminated soil directly while grazing (4, 5).

Medicinal plants like henna (Lawsonia inermis), moghat (Glossostemon bruguieri) and rosemary (Rosarinus officinalis) have been used for centuries, but very little is known about contaminants they may contain and the adverse effect they may have on human health.

Henna is a shrub, naturally grown or cultivated in a wide range of countries from north-east Africa to India. Marketed henna represents a natural material derived from dried and powdered leaves of the plant. Henna is applied in the form of paste to hair, skin, women's fingernails and parts of their feet as well as to men's beards. It imparts a reddish brown coloration lasting for up to 12 weeks. Henna was used as a hair dye as early as ancient times; for instance, the hair of Egyptian mummies was dyed with henna.

There are about 90 hair care products available on the market containing henna leaves, used and recommended as a hair tonic (6). Besides its use in cosmetics, henna also was used in Medieval Persian, Arab, Turkish and Jewish medicine to treat headaches, skin and teeth diseases, as well as animal bites.

Moghat, one of the most popular beverages in Egypt, is a shrub with thick, long, tapering, dark colored roots. After childbirth, women used hot drinks of powdered moghat as a general tonic and lactagogue. Moghat is also prescribed as a demulcent agent. Rosemary has been around for a long time, and therefore has a long list of claims regarding its medicinal uses, including use as a tonic, a digestive aid, to treat depression, headaches, and muscle spasms, and as an expectorant, promoter of menstrual flow, and stimulant for production of bile.

Limited data are available about the presence of environmental contaminants in medicinal plants (7, 8). Also few studies have been undertaken to determine the levels of PCDD/Fs in the environment or food in Egypt. They have focused mainly on fatty foods such as dairy products, fish and meat (9, 10).

In the present study, residues of of 17 PCDD/Fs and 12 D-L PCBs and 6 indicator PCBs were monitored in three commonly consumed medicinal plants when irrigated on fresh canal water and again when irrigated on wastewater. The main objective was to ascertain the relationship between irrigation water and the pollution load in the consumed parts of these medicinal plants.

MATERIAL AND METHODS

Agriculture

Rosemary, henna, and moghat shrubs were grown at the Suez Canal University farm, in sandy soil. Table 1 highlights the main properties of the university farm.

Table 1 Soil physical properties and chemical analysis at experimental site.

Physical properties
Sand	96.8
Silt	0.3
Clay	2.9
Chemical analysis
EC ds/m	0.8
PH	8.6
Ca^+ +	3.5
Mg^+ +	0.5
Na^+	3.9
K^+	0.4
CO3 ^− −	0.0
HCO3 ^−	3.2
Cl^−	3.2
SO4 ^− −	1.7
N mg/Kg	11.2
P mg/Kg	2.1
K mg/Kg	4.2

The plots were divided into two sections with one supplied with regular canal water for irrigation while the other was irrigated with raw municipal wastewater. Regular agricultural practices were observed simultaneously in the two sections. Land preparation was performed, including the addition of organic manure at a rate of 15 m³/acre. Manure was incorporated in soil, followed by irrigation, either with wastewater or canal freshwater. Seeds were planted at intervals of about 20 cm. Thinning was performed a few weeks later, then plants were fertilized using ammonia sulphate at a rate of about 250 kg/acre, super calcium phosphate at a rate of about 200 kg/acre and potassium sulphate at a rate of 75 kg/acre, then irriagation was performed again. Insect pest control measures were performed, using mainly organophosphorous insecticides.

Sampling

Medicinal plants were collected between 2007 and 2008. Fresh leaves of rosemary, henna, and moghat were collected and brought back to the laboratory. A total of 20 samples of each plant were collected at different plant growth stages pooled together before a composite sub-sample of 50 g dry w. was analyzed.

Analyses of PCDD/Fs and PCBs

Sub-samples of 50 g were analyzed for each of the 17 PCDD/Fs and 12 DL-PCBs, for which the WHO developed toxicity equivalency factors (TEFs) (11). Seventeen NDL-PCBs congeners were analyzed together with PCDD/Fs and DL-PCBs in one analytical procedure. High-resolution gas chromatography (HRGC)/high-resolution mass spectroscopy (HRMS) HP 6890 plus a gas chromatograph coupled to a Micromass Autospec Ultima mass spectrometer operating in EI mode at 35 eV and with a resolution of 10,000 (5% valley) was used.

Reagents and Procedure

Reagents used in this study were the same as described earlier (10). 50 g. homogenate were spiked with a series of 15 ¹³C₁₂-labeled 2,3,7,8 PCDD/F mix (EDF8999), a series of 12 ₁₃C₁₂-labeled PCB (EC4937), as internal standards, and then mixed with Spe-ed Matrix. The samples were extracted by sonication with n-hexane. The extracts were spiked with ₁₃C₁₂-labeled 2,3,7,8 PCDD (EDF6999) and with three ₁₃C₁₂-labeled PCB (EC4978) then cleaned up using the automatic three-column system, with pre-packed disposable columns containing multilayer silica, alumina and carbon. From this system two fractions were eluted, one with PCDD/Fs and the other with PCBs. Sample injections were performed in the splitless mode on a 60-m DB5 ms column (J&W 0.25 mm ID, 0.25 lm film) and on a 60-m Rtx 200 (Restek 0.25 mm ID, 0.25 lm film) for PCDD/Fs verification, and for PCBs verification on a 60 m DB5ms column (J&W 0.25 mm ID, 0.25 lm film) and on 30 m SPB-Octyl (Supelco 0.25 mm ID, 0.25 lm film). The quantification for PCDD/Fs and PCBs was carried out by isotope dilution methods, USEPA 1613 and 1668, respectively, using relative response factors previously obtained from five standard solution injections. Two ₁₃C₁₂-labeled PCDDs (EDF5999) and three ₁₃C₁₂-labeled PCBs (EC4979) were added to the extracts before injection for the recovery calculations of PCDD/Fs and PCBs, respectively.

The recovery has always ranged from 55 to 105%. Reproducibility was 15% for lower value or better. The laboratory blank, repeated twice every week, was lower than 8%, with respect to the minimum concentration found.

Calculation

PCDD/Fs and DL-PCBs TEQ are calculated using the TEFs according to WHO (11). Data below detection limit (LOD) were calculated as lower and upper bound values, assuming that all values of the different congeners are equal to zero or equal to their LOD, respectively.

Analytical Quality Assurance

PCDD/Fs and PCBs analyses were carried out in accredited laboratories (ISO/IEC 17 025). Interuniversity Consortium Chemistry for the Environment (INCA) Laboratory has successfully participated in interlaboratory studies since 2000 (Interlaboratory Comparison on PCDD/Fs, DL-PCBs and indicator PCBs in FOOD, Norwegian Institute of Public Health, Oslo, Norway).

RESULTS AND DISCUSSION

PCDD/Fs and DL-PCBs Congener Profiles

The concentrations and spectrum of of 7 PCDDs, 10 PCDFs, 4 non-ortho PCBs and 8 mono-ortho PCBs congeners in rosemary, moghat and henna samples are shown in Table 2. The sum of PCDDs, PCDFs and ratio sum PCDD/PCDFs are also included. Table 2 highlights the residue pattern in henna and rosemary samples when irrigated either with canal freshwater or wastewater. Residues are characterized by the dominance of PCDFs (PCDDs/PCDFs < 1), with a significant contribution of the lower (mono- to tri-) PCDF (average of 55% to PCDFs) in all samples. PCDFs dominated the typical fingerprints of combustion sources origin (12).

Table 2 Concentrations of PCDD/Fs and DL- PCBs (ng kg^{− 1} wet w) in medicinal plant samples irrigated with freshwater and wastewater.

		Henna		Rosemary		Moghat
Congener	WHO-TEF^1)	Irrigated with freshwater	Irrigated with wastewater	Irrigated with freshwater	Irrigated with wastewater	Irrigated with freshwater	Irrigated with wastewater
PCDDs
2,3,7,8-TeCDD	1	0.10 ± 0.03	0.55 ± 0.06	0.10 <	0.12 ± 0.08	0.05 <	0.05 ± 0.007
1,2,3,7,8-PeCDD	1	0.19 ± 0.008	0.28 ± 0.06	0.23 ± 0.05	0.26 ± 0.08	0.05 <	0.05 <
1,2,3,4,7,8-HxCDD	0.1	0.20 <	0.20 <	0.20 <	0.20 <	0.10 <	0.10 <
1,2,3,6,7,8-HxCDD	0.1	0.20 <	0.29 ± 0.01	0.20 <	0.20 ± 0.009	0.10 <	0.10 <
1,2,3,7,8,9-HxCDD	0.1	0.10 <	0.10 <	0.10 <	0.10 <	0.10 <	0.10 <
1,2,3,4,6,7,8-HpCDD	0.01	0.48 ± 0.1	0.55 ± 0.09	0.30 <	0.46 ± 0.3	0.15 <	0.15 <
OCDD	0.0001	1.40 ± 0.05	1.34 ± 0.007	1.18 ± 0.05	1.08 ± 0.02	0.35 ± 0.06	0.31 ± 0.02
PCDFs
2,3,7,8-TeCDF	0.1	1.35 ± 0.2	2.82 ± 0.07	2.63 ± 0.08	3.54 ± 0.02	0.06 ± 0.05	0.07 ± 0.02
1,2,3,7,8-PeCDF	0.05	1.38 ± 0.05	1.77 ± 0.2	2.21 ± 0.5	2.95 ± 0.009	0.05 ± 0.02	0.06 ± 0.01
2,3,4,7,8-PeCDF	0.5	1.14 ± 0.1	1.45 ± 0.006	1.55 ± 0.06	2.10 ± 0.007	0.05 ± 0.02	0.06 ± 0.007
1,2,3,4,7,8-HxCDF	0.1	1.23 ± 0.09	1.03 ± 0.04	0.96 ± 0.08	1.34 ± 0.04	0.10 <	0.10 <
1,2,3,6,7,8-HxCDF	0.1	0.92 ± 0.2	0.95 ± 0.08	0.83 ± 0.09	1.14 ± 0.07	0.10 <	0.10 <
2,3,4,6,7,8-HxCDF	0.1	0.59 ± 0.06	0.54 ± 0.04	0.52 ± 0.1	0.51 ± 0.2	0.10 <	0.10 <
1,2,3,7,8,9-HxCDF	0.1	0.24 ± 0.06	0.20 <	0.20 <	0.20 <	0.10 <	0.10 <
1,2,3,4,6,7,8-HpCDF	0.01	2.77 ± 0.3	1.22 ± 0.05	0.94 ± 0.2	1.08 ± 0.07	0.15 <	0.15 <
1,2,3,4,7,8,9-HpCDF	0.01	0.50 ± 0.09	0.30 <	0.30 <	0.30 <	0.15 <	0.15 <
OCDF	0.0001	4.96 ± 0.8	0.60 <	0.60 <	0.60 <	0.30 <	0.30 <
Sum PCDDs		2.17	3.01	1.41	2.12	0.35	0.31
Sum PCDFs		15.08	9.78	9.64	12.66	0.16	0.19
Sum PCDDs/PCDFs		0.144	0.308	0.146	0.167	2.19	1.63
Dioxin-like PCBs
Non-ortho PCBs
77∗ 3,4,5,3′-TCB	0.0001	30 ± 5.2	29 ± 3.9	39 ± 6.4	97 ± 6.6	8 ± 0.9	7 ± 1
81∗ 3,4,3′,4′-TCB	0.0001	5 <	5 <	5 <	8 ± 1.2	5 <	5 <
126∗ 3,4,5,3′,4′-PeCB	0.1	5 <	5 <	5 ± 1	7 ± 1.1	5 <	5 <
169∗ 3,4,5,3′,4′,5′-HxCB	0.01	5 <	5 <	5 <	5 <	5 <	5 <
Mono-ortho PCBs
123∗ 2,4,5,2′,4′-CB	0.0001	7 ± 0.85	10 ± 0.9	14 ± 2.8	18 ± 1.4	5 <	5 <
118∗ 2,4,5,3′,4′-PeCB	0.0001	129 ± 23.9	227 ± 31.8	157 ± 23.8	275 ± 28.9	0.031 ± 0.01	0.034 ± 0.008
114∗ 2,3,4,5,4′-PeCB	0.0005	5 ± 0.4	8 ± 0.9	6 ± 1	10 ± 1.2	5 <	5 <
105∗ 2,3,4,3′,4′-PeCB	0.0001	52 ± 12	87 ± 11	62 ± 14	117 ± 21	0.012 ± 0.005	0.012 ± 0.002
156∗ 2,3,4,5,3′,4′-HxCB	0.0005	8 ± 1.7	16 ± 1.5	10 ± 1	14 ± 0.8	5 <	5 <
157∗ 2,3,4,3′,4′,5′-HxCB	0.0005	5 <	5 <	5 <	5 <	5 <	5 <
167∗ 2,4,5,3′,4′,5′-HxCB	0.00001	5 ± 1	11 ± 1.6	9 ± 1.8	13 ± 1.7	5 <	5 <
189∗ 2,3,4,5,3,4,5-HxCB	0.0001	5 <	5 <	5 <	5 <	5 <	5 <
1)Van den Berg et al., 1998

The dominance of the lower PCDFs has been reported in chimney soot samples arising from wood burning (13), and the UK ambient air samples from an area where the domestic burning of wood and coal is common (14). TeCDF was the predominant congener in fire products after accidental fires (15). Rappe et al. (1989) have listed 2,3,7,8-TCDF and 1,2,3,6,7,8-HxCDD isomers have been listed as indicators of a typical “sewage sludge pattern” (16). It is worth mentioning that congener 2,3,7,8-TCDF has the highest contribution to PCDFs group in all the samples irrigated with wastewater in this study.

OCDF was only detected in henna samples irrigated with freshwater and the highest concentration of 1,2,3,4,6,7,8-HpCDF was also reported in the same samples. This result reflects the non-industrialized nature of Ismailia city, as the source of OCDF is mainly chemical manufacturing, especially polyvinylchloride (PVC) manufacturing processes (17). The high concentration of OCDF detected in henna samples irrigated with freshwater could be explained by the contamination of irrigation water itself.

In Egypt, some industrial facilities unlawfully discharge their waste in agricultural drains and it eventually ends up in some irrigation canals, thus contaminating crops.

The low contribution of OCDD, reported in henna and rosemary (7–10% to PCDD/Fs), is implying that the source of contamination is not mainly an atmospheric deposition that tends to enrich the OCDD congeners in comparison with the less chlorinated congeners, because of its lower photodegradation potential (18). It is mainly deposited through airborne particles and/or bound to soil since it has very low environmental movement through volatilization, leaching or degradation in comparison to other congeners in soil (19). Therefore it has been reported as the dominant congener group in urban and rural soils.

Table 2 also showed that the OCDD concentrations were similar in henna and rosemary whether irrigated with freshwater or wastewater, suggesting that the soil itself is the origin of this congener.

OCDD has been reported to be dominant in domestic combustion emissions (20). OCDD has also been reported as the most abundant congener in open fire of garden waste (21). It is worth mentioning that in henna samples, the concentration of the most toxic congener (TeCDD) was 5 times higher in wastewater irrigated samples than freshwater irrigated samples, with concentrations ranging between under or very close to detection limits in the case of moghat and rosemary respectively. PCDDs profile reported for henna and rosemary irrigated with wastewater is dominated by 1,2,3,4,6,7,8-HpCDD and OCDD, with notable resemblance to the profile obtained from sewage sludge from different areas in Spain (22). The table also showed that moghat samples, whether irrigated with freshwater or wastewater, had a different profile, however OCDD was the only detectable congener in the PCDDs group (contributing 100% to total PCDDs).

It has been reported that emissions from domestic combustion are dominated by higher chlorinated dioxins, in particular OCDD (20). For the PCDFs group, the lower (mono- to tri-) PCDFs were the only detectable congeners. The ratio of PCDDs/PCDFs was higher than one. Finally the concentrations of many congeners in moghat samples were very close to or below the analytical limit of detection, indicating the weak ability of this plant to accumulate PCDD/Fs either from the atmosphere, irrigation water or the soil. This result suggests that the origin of the dioxin in the moghat plants was uptake from the atmosphere while absorption of dioxins from the wastewater or soil via the roots is extremely unlikely.

Finally, congener profiles of PCDD/Fs in investigated samples seems to be a “blend” of emissions from various combustion types like wood burning, coal burning and accidental fires. These results clearly reflect the situation in Egypt, where domestic and some agricultural solid waste open burning is a common practice, and about one fifth of the municipal solid waste is burned in open dump sites all over the country. The present study suggests that these processes are the main sources for dioxin emission in Egypt.

Levels of PCDD/Fs and DL-PCBs

WHO-TEQ concentrations in plant samples irrigated with freshwater and wastewater are summarized in Table 3 and range from lower to upper bound values based on wet w. PCDDs, PCDFs and DL-PCBs residues were higher in wastewater irrigated samples than freshwater irrigated samples in the case of rosemary and henna. Results also indicated that moghat samples grown on either freshwater or wastewater had similar dioxin content and similar congeners profile with very low contamination levels.

Table 3 Concentrations of PCDDs, PCDFs, and DL-PCBs TEQ (pg WHO-TEQ/g) based on wet w.

	PCDDs TEQ		PCDFs TEQ		DL-PCBs TEQ
Sample	Irrigated with freshwater	Irrigated with wastewater	Irrigated with freshwater	Irrigated with wastewater	Irrigated with freshwater	Irrigated with wastewater
Henna	0.295–0.345	0.865–0.895	1.105–1.105	1.360–1.383	0.028–0.0286	0.047–0.048
Rosemary	0.230–0.383	0.407–0.436	1.39–1.41	1.861–1.884	0.535–0.535	0.764–0.764
Moghat	0.00004–0.132	0.000031–0.132	0.034–0.077	0.040–0.083	0.005–0.0057	0.005–0.007
Data present a range from lower to upper bound values.

Variation in the WHO TEQ concentration calculated for henna, rosemary, and moghat may reflect their different PCDD/Fs and DL-PCBs accumulation capacities. This result is not in line with Beck et al. (1994) who reported that dioxin concentrations were unlikely to differ largely between vegetables samples grown in a contaminated area and those in a background area (23). This, in turn would imply that vegetables substantially lack capability for dioxin bioaccumulation owing to their low lipid content, unlike foods with high lipid content such as fish, meat and dairy products.

Uegaki et al. (2006) have reported that the TEQ for dioxins in milled rice was 0.0040 pg-TEQ/g, and absorption of dioxins from the soil into the rice via the roots is extremely unlikely, confirming that the sources of the dioxin pollution were the atmospheric gas phase and adhesion of the soil (24). On the other hand Hülster et al. (1994) reported that dioxins are transferred from the soil to vegetables of the cucumber family, suggesting that plants in the cucumber family may have some special ability (25).

The pathways by which water-borne chemicals may enter plants are via root uptake from the soil solution and subsequent translocation in the transpiration stream, and adsorption by roots and shoots of volatilize hydrophobic organic compounds (HOCs) from the soil. Most of the studies suggest that the origin of the dioxins in the plants was uptake from the atmospheric gas phase rather than absorption from the soil via the roots. Several studies have shown that root uptake and translocation to vegetative parts of sludge-borne HOCs, including PCBs, PCDDs/Fs and polycyclic aromatic hydrocarbons (PAHs) is low in plants (26, 27, 28). This is due to high n-octanol/water partition coefficients and strong sorption of HOCs to soil particles and organic matter.

One exception to the low plant availabilities of HOCs is carrots, which can accumulate HOCs in the root peel when grown in sewage sludge (26, 29). Carrots therefore have often been selected as the worst case candidates for uptake of HOCs from soil (Engwall et al., 1996, 1997).

Although translocation of non-ionic organic compounds from the roots to shoots is negligible due to the low water solubility, high n-octanol/water partition coefficients and strong sorption of many compounds to soil particles/organic matter. It could happen that wastewater or sewage sludges may contain surfactants that may enhance the solubility of some compounds and facilitate root uptake (30). Therefore, special care has to be taken with the concentration and the application rate of this type of organic contaminant in sludge that will be applied in agronomic interest soils.

Figure 1 presents the lower bound values of the total TEQ (PCDD/Fs + DL-PCBs) in all samples. Among the analyzed samples, rosemary showed the highest concentration (3.03 ng TEQ/kg wet w) followed by henna (2.27 ng TEQ/kg wet w) and moghat (0.055 ng TEQ/kg wet w).

Figure 1 Contribution of PCDDs, PCDFs and DL-PCBs to the total TEQs based on lower bound values.

Reports of dioxin resides in medicinal plants are quite meaegr, but abundant in fatty food. A number of studies were reported about dioxin residues in leafy vegetables. PCDD/Fs were detected at 0.15–0.40 ng TEQ/kg d.m. in Chinese green tea (31), 0.082 pg TEQ/g in Korean cabbage (32) and at 0.1–0.3 pg I-TEQ/g in lettuce of the UK (33). In carrots the dioxin concentrations were increased up to seven times when grown in soil amended with high applications of some of the sludge samples, while in the cucumbers, a more than two-fold increase was observed in specimens grown in sludge–amended soil when compared to controls, suggesting a small uptake from the roots to the shoots (3).

Nakagawa et al. (2002) reported that the mean levels of dioxins in the edible portions were 0.09 pg TEQ/g in spinach, 0.13 pg TEQ/g in garland chrysanthemum, 0.01 pg TEQ/g in marsh parsley and 0.01 pg TEQ/g in Brassica Campestris (34).

The major food sources of PCDD/Fs have been reported to be fat-containing animal products, such as fish and shellfish (35). Therefore the European Commission first introduced regulatory limits for dioxins in food in 2001. And the current EU regulation set action levels for PCDD/Fs and DL-PCBs of 0.4 ng TEQ/kg product and 0.2 ng TEQ/kg product respectively in fruits and vegetables/cereals (36).

Figure 1 showed that residues of the PCDD/Fs in henna and rosemary are at least 3 times higher than the action level set by the EU for PCDD/Fs, and many times higher than levels reported for plants in other studies.

It is of high interest to evaluate the relative abundance of PCDD/Fs and DL-PCBs with regard to the total TEQ value. The contribution from the DL-PCBs group to the total TEQ in the samples irrigated with freshwater and wastewater are depicted in Figure 1. Generally, the contribution to total TEQ values (PCDD/Fs+DL-PCBs) has an average of 25%, 7% and 2% for the rosemary, moghat and henna, respectively, demonstrating the lower importance of this group to the total TEQ evaluation in plant samples.

For non-ortho PCBs, although the 126 PCB is the most toxic, having the highest TEF and accounting for the larger contribution of PCBs to the TEQ, it does not contribute to the total PCBs in this study, and congener 77 PCB is more or less the main contributor to this group in all samples. Most of Mono-ortho PCB congeners were detected in henna and rosemary samples, with penta-CB as the main contributor. Meanwhile congener 118 was the most abundant, followed by congener 105, and PCB77 (Table 2). The profile reported in this study for Mono-ortho PCBs is in accordance with previously reported profile for foodstuffs from the same city in Egypt (10), and the profile reported in five different plants by Jin-Juh Jou et al. (37).

Levels and Patterns of NDL-PCBs

Table 4 presents the concentrations of different NDL-PCBs congeners in the studied samples, the sum of six indicator, the total of 17 PCBs and the ratio six indicator/total PCB. Indicator PCBs are known to be persistent in the environment and to bioaccumulate in the food chain, and are assumed to be a suitable representative for all PCBs (38). The present results are in line with this opinion as the ratio sum six indicator/total PCBs was an average of 75% in all the analyzed samples.

Table 4 Concentrations of NDL-PCBs (ng/g wet w) in medicinal plant samples from Ismailia, Egypt.

	Henna		Rosemary		Moghat
PCB Congener IUPAC No	Irrigated with freshwater	Irrigated with wastewater	Irrigated with freshwater	Irrigated with wastewater	Irrigated with with water	Irrigated with wastewater
∗118-CB	0.129 ± 0.02	0.227 ± 0.07	0.157 ± 0.08	0.275 ± 0.05	0.031 ± 0.01	0.034 ± 0.001
∗28-CB	1.231 ± 0.13	1.814 ± 0.2	2.475 ± 0.8	4.196 ± 0.5	0.411 ± 0.004	0.362 ± 0.01
∗52-CB	0.395 ± 0.04	0.608 ± 0.08	0.721 ± 0.2	1.001 ± 0.06	0.139 ± 0.07	0.104 ± 0.005
∗101-CB	0.156 ± 0.01	0.227 ± 0.08	0.231 ± 0.06	0.316 ± 0.04	0.04 ± 0.01	0.035 ± 0.001
∗153-CB	0.1 ± 0.003	0.199 ± 0.06	0.139 ± 0.03	0.189 ± 0.04	0.025 ± 0.007	0.029 ± 0.004
∗138-CB	0.088 ± 0.002	0.164 ± 0.03	0.12 ± 0.02	0.151 ± 0.02	0.022 ± 0.002	0.025 ± 0.005
∗180-CB	0.024 ± 0.001	0.058 ± 0.002	0.036 ± 0.005	0.049 ± 0.005	0.008 ±.002	0.009 ± 0.003
95-CB	0.13 ± 0.001	0.195 ± 0.06	0.204 ± 0.06	0.234 ± 0.04	0.033 ± 0.005	0.025 ± 0.006
99-CB	0.063 ± 0.002	0.10 ± 0.03	0.089 ± 0.01	0.15 ± 0.05	0.017 ± 0.002	0.014 ± 0.005
110-CB	0.127 ± 0.06	0.19 ± 0.05	0.168 ± 0.03	0.24 ± 0.05	0.029 ± 0.004	0.027 ± 0.008 >
151-CB	0.035 ± 0.006	0.049 ± 0.02	0.049 ± 0.001	0.056 ± 0.003	0.006 ± 0.001	0.007 ± 0.002
149-CB	0.106 ± 0.04	0.163 ± 0.07	0.139 ± 0.03	0.161 ± 0.01	0.022 ± 0.003	0.022 ± 0.01
146-CB	0.019 ± 0.005	0.036 ± 0.02	0.03 ± 0.002	0.043 ± 0.005	0.005 >	0.005 ± 0.002
187-CB	0.016 ± 0.004	0.031 ± 0.01	0.021 ± 0.001	0.031 ± 0.004	0.005 >	0.005 ± 0.001
183-CB	0.01 ± 0.001	0.021 ± 0.01	0.013 ± 0.001	0.022 ± 0.006	0.005 >	0.005 >
177-CB	0.008 ± 0.002	0.013 ± 0.006	0.023 ± 0.002	0.016 ± 0.005	0.005 >	0.005 >
170-CB	0.016 ± 0.005	0.031 ± 0.008	0.02 ± 0.004	0.026 ± 0.002	0.005 >	0.006 ± 0.002
Sum 6 indicator PCBs	1.99	3.07	3.72	5.90	0.65	0.56
Total 17 PCBs	2.65	4.13	4.64	7.16	0.78	0.71
6 indicator/total PCB (%)	75	74	80	82	82	80
Note.
Data below the limit of detection (LOD) are considered as zero.

Results also indicated that the NDL-PCBs concentrations increased in both the henna and rosemary samples irrigated with wastewater compared to the samples irrigated with freshwater. The sum concentration of 17 PCBs congeners increased from 2.65 to 4.13 ng/kg wet w in henna, and from 4.64 to 7.16 ng/kg wet w in rosemary. In moghat samples no difference was observed between freshwater and wastewater irrigated samples.

Congener PCB 28 was the main contributor to the sum of 6 indicators with an average of about 60% in all samples, followed by PCB 52 and PCB 101 contributing an average of 18% and 6% to sum 6 indicators in all samples respectively.

CONCLUSION

The preset study constitutes the first baseline information for the level and profiles of PCDD/Fs, DL-PCBs and NDL-PCBs in some medicinal plants (henna, rosemary and moghat) when irrigated with crude wastewater or canal freshwater.

Residues showed that all the studied contaminants were much higher in henna and rosemary plants irrigated with wastewater, while in the case of moghat samples, no difference was observed between freshwater irrigated samples and wastewater irrigated samples. The congener profiles of PCDD/Fs in investigated samples seem to be a “blend” of emissions from various combustion types like wood burning, coal burning and accidental fires, and reflect the non-industrialized nature of the city. Finally, additional studies are urgently needed to investigate the levels of PCDD/Fs and DL-PCBs in the most commonly used vegetables/plants after using wastewater for irrigation and to calculate the risk for consumers.

ACKNOWLEDGEMENT

This study was supported and the analytical part was conducted by Interuniversity Consortium of Chemistry for the Environment (INCA), Italy. Special thanks to Professor P. Tundo, and Dr. S. Raccanilli. Thanks are also due to Professor E. Qouraish from the Horticulture Department, Faculty of Agriculture, Suez Canal University, Ismailia, Egypt, for supplying medicinal plant samples.

Notes

∗Numbers with asterisk are the PCBs IUPAC no.

∗Six indicator PCBs: CB 28, 52, 101, 153, 138 and 180.