Determination of polycyclic aromatic hydrocarbons (PAHs) in carbon black-containing plastic consumer products from the Jordanian market

Abstract

The concentrations of 13 Polycyclic Aromatic Hydrocarbons (PAHs) were determined using a developed and validated Gas Chromatography/Mass Spectrometry (GC/MS) method in 12 carbon Black-containing rubber and plastic samples collected from the Jordanian market. The total concentrations of the studied PAHs were ranged from 1.25 mg/kg to 528 mg/kg. Both results of Toxicity Equivalent concentration (TEQ) and those of the total estimated cancer risk show that the most dangerous and carcinogenic type of carbon-black containing plastic article is the toy wheel, and the least carcinogenic are the car wiper and toilet plunger samples. The validation parameters were applied on the developed method; the correlation coefficient in linearity test for the 13 PAHs were ranging from 0.9993 to 0.9998 for the concentration range 0.01 to 5 mg/L. Recovery results were ranging between 81.2% and 129%.

Keywords:

• PAHs
• plastic consumer products
• carbon Black
• cancer risk
• TEQ
• Jordan

1. Introduction

Polymers are large molecules, which consist of a large number of small molecules that are linked together through a polymerization process. They are classified into two categories; thermosets and thermoplastics, the later is commonly called as plastics (Skoog et al. 1997).

Plastic mechanical properties are enhanced using additives, which are introduced during plastic manufacturing. Additives include fillers, colorants, plasticizers, and stabilizers. Carbon black is used as a filler and colorant (Skoog et al. 1997).

Carbon black is produced during the incomplete combustion of carbon containing materials such as coal and wood, and it is produced under controlled conditions with specific properties (Donnet 1993). Carbon black properties (such as particle size, structure, and surface area) control the resulted properties of the products like rubber and plastic. In general, smaller particle size gives better reinforcing and abrasion resistance qualities (Crump 2000).

Polycyclic Aromatic Hydrocarbons (PAHs) are a large group of compounds that consists of carbon and hydrogen only, with two or more fused rings (World Health Organization 2000) hence, they are a class of organic compounds produced by incomplete combustion or high-pressure processes (Agency for Toxic Substances and Disease Registry 1995), by which carbon black is manufactured and PAHs are found to be bounded to carbon black (International Carbon Black Association 2014).

PAHs are solids that have low vapor pressure (low volatility) at room temperature (Agency for Toxic Substances and Disease Registry 1995), have relatively low solubility in water, and highly lipophilic (World Health Organization 2000).

PAHs were proved to cause skin and bladder cancer for chimney sweeps and tar workers, as they were exposed to considerable amounts of PAHs during their work (World Health Organization 2000).

According to the Environmental Protection Agency (Environmental Protection Agency 2008), a number of PAHs caused tumors when laboratory animals were exposed to them by feeding, breathing, or applying to the skin (Crump 2000).

The EU regulation REACH (Registration, Evaluation, Authorization and Restriction of the Chemicals) (European Union 2013) No 1907/2006 has restricted the concentrations of PAHs in consumer articles to be less than 1 mg/kg, due to the health risk whether for prolonged or short term direct contact. This regulation was amended with the regulation (EU) No. 1272/2013 as follows: Toys and child care articles 0.5 mg/kg each; all other articles supplied to general public (sport equipment, trolleys, footwear, gloves, watch straps, masks, and head bands) 1.0 mg/kg each. This new requirement is applicable from December 27 2015.

Previous studies on polycyclic aromatic hydrocarbon were performed to determine the concentration of these compounds contaminating different matrices such as air, soil, and oil shale, in the Jordanian environment.

Zarqa city contains 52% of the industries in Jordan, including national refinery complex and Al-Hussein thermal power station, therefore, air is significantly polluted with PAHs. PAHs with low molecular weights (e.g. phenanthrene, fluorine, and chrysene) were found mostly in air samples. Yousef et al. have analyzed thirty air samples for PAHs. They found that the total average air concentration of PAHs is the highest for fluorine (71.2 ng/m³) and the lowest for benzo(a)pyrene (7.4 ng/m³) (Yousef et al. 2012).

Tarawneh et al. (2012) carried out a study to determine the concentration of thirteen PAHs in 23 samples collected from the vicinity of the Jordan petroleum refinery and Al-Hussein thermal power stations in Zarqa region. They found that the total concentration for PAHs was ranged between 0.94 µg/kg and 191 µg/kg.

According to the study of oil shale, samples were collected from the major deposit sites in Jordan and they were heated at different temperature ranges then analyzed to determine the concentration of PAHs, the lowest temperature range (200–400 °C) gave the highest PAHs concentration (75.99–317.53 µg/kg) while the highest temperature range (600–800 °C) samples were not containing any PAHs (Al-Tarawneh 2014).

Concentrations of PAHs were determined in oil shale using three samples from each of the eight locations in Jordan from depth of 30 to 85 m. PAHs concentrations were found to be between 0.093 and 2.22 mg/kg (Alawi and Tarawneh 2015).

There are very limited research works about the PAHs concentrations in carbon black-containing plastic consumer products. Moon et al. (2014) have studied four consumer products (grips of a bag and a hammer; a cable and a plastic sandal) on the amounts and the kinds of PAHs. Fifteen kinds of PAHs including phenanthrene were detected in the hammer grip with concentration range between 8.5 mg/kg (acenaphthylene) and 83.4 mg/kg (phenanthrene).

2. Materials and methods

2.1 Chemicals and reagents

An EPA 525 certified reference standard mixture of 1 ml containing 500 mg/L of each of 13 components in dichloromethane was purchased from Supelco (Bellefonte, PA). These compounds are as follows: Acenaphthylene, Fluorene, Phenanthrene, Anthracene, pyrene, Benzo(a)anthracene, Chrysene, Benzo(b)fluoran-thene, Benzo(k)fluoranthene, Benzo(a)pyrene, Indeno(1, 2,3-cd)pyrene, Dibenzo(a,h)anthracene, and Benzo(g,h,i) perylene. The Internal standard used was 1-fluronaphthalene of the purity 99% and was purchased from Aldrich (St. Louis, MO).

Hypersep C18, 500 mg cartridges with 3 ml capacity, purchased from Thermo Scientific (Waltham, MA) were used for extract cleanup.

Solvent used is n-Hexane (ACS grade, purity >95%) was purchased from TEDIA (Fairfield, OH).

2.2 Sampling

Samples were collected to represent the Jordanian market; these were purchased from different stores in the downtown market of Amman city.

Collected samples were as follows: Gloves, mouse pad, car wiper, rubber shoe, bicycle grip, toilet plunger, car mat, gas O-ring, gas tube, used car mat, toy wheel, and electrical wire.

2.3 GC/MS apparatus and working conditions

A Gas chromatograph type Agilent 6890 series II with Auto sampler injector series 7683 was used under the following conditions:

• Injection volume: 2 μL/splitless.

• Column: BBX-5 (30 cm ×0.25 mm I.D. × 0.25 μm film thickness).

• Carrier gas: Helium (99.999%), (8 psi)

• Temperature program 100 °C (10 min), 100–160 °C (25 °C/min), 160–270 °C (5 °C/min), 270 °C isotherm (27 min)

• Detector: mass selective quadruple – detector, Agilent 5973 N (MSD)

• Auxiliary (transfer line): 280 °C, Electron Impact Ionization.

• Ionization Energy: 70 eV.

• Calibration substance: Perflourotributylamine (PFTBA)

• Tuning masses: 69/219/502

• Acquisition mode: Selective ion monitoring (SIM) – mode.

• Data analysis: HP MSD productivity Chemstation SW.

2.4 Qualitative and quantitative identification

In addition to the information obtained from the GC/MS library according to m/z ratio as shown in Table 1 (Peters and Harlin 1995), the peak of each analyte in the sample chromatogram was identified by comparing its relative retention time (RRT) with the RRT of the analyte in the chromatogram of the standard mixture. The quantitative calculation for each compound was done by comparing its relative peak area (RPA) in the sample chromatogram with its (RPA) in the chromatogram of the standard mixture using the one-point calibration method.

Table 1. PAHs quantitation masses, according to Peters and Harlin (1995).

PAH	m/z	PAH	m/z
1-Fluoronaphthalene	146	Chrysene	228
Fluorenthene	202	Benzo(b)fluoranthene	252
Fluorene	166	Benzo(k)fluoranthene	252
Phenanthrene	178	Benzo(a)pyrene	252
Anthracene	178	Ineno(1,2,3-cd)pyrene	276
Pyrene	202	Dibenzo(a,h)anthracene	278
Benzo(a)anthracene	228	Benzo(g,h,i)perylene	276

2.5 Sample extraction and clean-up

The extraction method for PAHs from plastic material was adopted from the work of Rios (Rios et al. 2010). 500 mg of the homogenized sample was weighed in order to extract PAHs from plastic and rubber; it was done using n-hexane as solvent in Soxhlet apparatus, for a period of 8 h. The extract was then evaporated by using rotary evaporator at 40 °C and 335 mbar to about 3 ml.

The residues from the extraction step were added to the C18 solid phase extraction (SPE) apparatus and eluted with 23 ml n-hexane. The eluant was evaporated at 40 °C and 335 mbar to ca. 1 ml, then to dryness using a gentle stream of nitrogen. The residue was dissolved in 1 ml n-hexane containing 1 µg/mL internal standard (1-fluoronaphthalene), and then 1 µL was injected onto the GC/MS column.

3. Method validation

3.1 Linearity range

The thirteen compounds of PAHs were found to be linear in the range 0.01–5 µg/mL using 6 concentration levels. Coefficient of determination values for the 13 PAH component was ranging between 0.9993 and 0.9998, which indicates a good linearity in the concentration range.

3.2 Detection limit and quantitation limit

The detection limit (DL) is defined as the minimum concentration which gives S/N value equals 3, and the quantitation limit (QL) is the minimum concentration which gives S/N value equals 10.

Instrument DL and QL were calculated using standard mixture injection, see Table 2. And method detection limit (MDL) and method quantitation limit (MQL) were calculated using blank spiked with standard mixture, see Table 3.

Table 2. PAHs retention time and instrumental DL and QL.

Number	PAH	tR (min)	DL (µg/mL)	QL (µg/mL)
1	Fluorene	16.95	0.0003	0.0010
2	Phenanthrene	20.36	0.0003	0.0009
3	Anthracene	20.56	0.0003	0.0010
4	Fluoranthene	25.32	0.0005	0.0018
5	Pyrene	26.30	0.0005	0.0016
6	Benz[a]anthracene	31.85	0.0007	0.0023
7	Chrysene	32.01	0.0008	0.0026
8	Benz[b]fluoranthene	37.30	0.0011	0.0037
9	Benzo[k]fluoranthene	37.46	0.0012	0.0040
10	Benzo[a]pyrene	39.48	0.0021	0.0069
11	Indeno(1,2,3-c,d)pyrene	50.22	0.0018	0.0061
12	Dibenz[a,h]anthracene	50.79	0.0017	0.0056
13	Benzo[g,h,i]perylene	53.57	0.0089	0.0298

Table 3. PAHs retention time, MDL and MQL.

Number	PAH	tR (min)	MDL (µg/g)	MQL (µg/g)
1	Fluorene	16.23	0.0015	0.0049
2	Phenanthrene	19.38	0.0016	0.0037
3	Anthracene	19.54	0.0014	0.0046
4	Fluoranthene	24.09	0.0025	0.0082
5	Pyrene	24.98	0.0024	0.0082
6	Benz[a]anthracene	30.41	0.0023	0.0077
7	Chrysene	30.58	0.0024	0.0080
8	Benz[b]fluoranthene	35.14	0.0042	0.0355
9	Benzo[k]fluoranthene	35.25	0.0048	0.0225
10	Benzo[a]pyrene	36.59	0.0088	0.0205
11	indeno(1,2,3-c,d)pyrene	43.69	0.0062	0.0207
12	Dibenz[a,h]anthracene	44.09	0.0105	0.0285
13	Benzo[g,h,i]perylene	45.60	0.00445	0.0190

3.3 Recovery

Recovery, which represents method precision, was checked through preparing three different concentrations of low, medium, and high in blank spiked with the standard mixture, to get final concentrations of 1, 2, and 10 mg/kg. For each level, three samples were prepared. Recovery results were ranging between 81.2% and 129%. and the relative standard deviations were ranging between 0.64 and 14.1%.

4. Results

4.1 Concentration of PAHs in real samples

The rubber and plastic samples were analyzed according to the above mentioned and validated method. Each sample was analyzed three times and each extract was injected onto the GC/MS column three times. Table 4 shows the average concentrations of PAHs in the samples.

Table 4. Concentration of PAHs in the real samples (Average concentration in mg/kg ± standard deviation).

	Sample type
PAH	Gloves	Mouse pad	Car wiper	Rubber shoe	Bicycle grip	Toilet plunger	Car mat	Gas O-ring	Gas tube	Used car mat	Toy wheel	Electrical wire
Fluorene	0.3 ± 0.0	67 ± 2.4	6 ± 0.4	12 ± 0.9	148 ± 3.1	7 ± 2.4	ND^a	31 ± 3.5	12 ± 0.6	12 ± 1.1	14 ± 0.6	0.4 ± 0.0
Phenanthrene	0.3 ± 0.0	99 ± 1.0	3 ± 0.2	6 ± 0.6	177 ± 2.1	7 ± 0.4	0.2 ± 0.0	47 ± 4.5	14 ± 0.7	27 ± 2.0	98 ± 0.6	1.4 ± 0.2
Anthracene	0.1 ± 0.0	20 ± 2.1	0.6 ± 0.	0.9 ± 0.1	36 ± 1.4	1 ± 0.1	ND	12 ± 1.6	3 ± 0.3	5 ± 0.4	2 ± 0.5	ND
Fluoranthene	0.2 ± 0.0	24 ± 1.4	0.2 ± 0.0	0.5 ± 0.1	14 ± 0.5	2 ± 0.7	ND	8 ± 0.5	1 ± 0.1	31 ± 2.5	30 ± 0.6	0.9 ± 0.1
Pyrene	0.5 ± 0.0	13 ± 1.4	0.8 ± 0.0	0.4 ± 0.1	7 ± 0.9	1 ± 0.2	ND	9 ± 0.5	1 ± 0.1	28 ± 2.4	147 ± 1.3	1.2 ± 0.2
Benz[a]anthracene	ND	5 ± 0.9	ND	ND	ND	ND	ND	0.2 ± 0.0	ND	17 ± 1.3	124 ± 3.0	0.1 ± 0.0
Chrysene	ND	6 ± 1.3	ND	ND	ND	ND	ND	0.2 ± 0.0	ND	26 ± 2.0	99 ± 2.4	0.1 ± 0.0
Benz[b]fluoranthene	0.1 ± 0.0	0.7 ± 0.1	ND	ND	ND	ND	ND	ND	ND	21 ± 3.4	ND	9 ± 0.8
Benzo[k]fluoranthene	ND	ND	ND	ND	ND	ND	ND	ND	ND	15 ± 3.4	ND	ND
Benzo[a]pyrene	ND	ND	ND	ND	ND	ND	3 ± 0.2	ND	ND	15 ± 1.4	33 ± 2.4	ND
indeno(1,2,3-c,d)pyrene	ND	ND	ND	0.2 ± 0.0	ND	ND	ND	ND	ND	9 ± 0.9	ND	ND
Dibenz[a,h]anthracene	ND	ND	ND	0.1 ± 0.0	ND	ND	ND	ND	ND	2 ± 0.2	ND	ND
Benzo[g,h,i]perylene	ND	ND	ND	0.1 ± 0.0	ND	ND	ND	1 ± 0.1	ND	13 ± 1.2	ND	ND
∑PAHs ± SD	1.5 ± 0.0	235 ± 2.6	11 ± 0.4	20 ± 1.2	382 ± 3.2	18 ± 2.4	3 ± 0.2	107 ± 3.5	31 ± 0.6	221 ± 7.1	547 ± 4.9	13 ± 0.8

^a ND: not detected.

4.2 Toxicity equivalency concentrations for PAHs in real samples

Toxicity equivalency factor (TEF) evaluation is a method that is used to determine the toxicity of PAH compounds relative to Benzo[a]pyrene (BaP). Toxicity equivalent concentration (TEQ) is calculated by the summation of the products of TEF value times the concentration of PAH, as in the following equation (Lee 2010):

Where:

TEQ: toxic equivalent concentration.

C_i: concentration of the ith PAH.

Table 5 shows the concentrations of PAHs in (ng TEQ/g) for the real samples.

Table 5. Concentrations of PAHs in (µg TEQ/kg) for real samples.

PAHs	TEF^a	Sample 1 (Gloves)	Sample 2 (Mouse pad)	Sample 3 (Car wiper)	Sample 4 (Rubber shoe)	Sample 5 (Bicycle grip)	Sample 6 (Toilet plunger)	Sample 7 (Car mat)	Sample 8 (Gas O-ring)	Sample 9 (Gas tube)	Sample 10 (Used car mat)	Sample 11 (Toy wheel)	Sample 12 (Electrical wire)
Fluorene	0.001	0.3	67	6.2	12	148	7	–	31	12.34	12	14	0.4
Phenanthrene	0.001	0.3	99	2.6	6	177	7	0.2	47	13.84	27	98	1.4
Anthracene	0.01	1.0	199	56	90	360	10	–	120	28.10	50	20	–
Fluoranthene	0.001	0.2	24	0.2	0.5	14	2	–	8	1.10	31	30	0.9
Pyrene	0.001	0.5	13	0.8	0.4	7	1	–	9	0.74	28	147	1.2
Benzo[a]anthracene	0.1	2.0	490	–	–	–	–	–	20	–	1700	12,400	10
Chrysene	0.01	0.3	60	–	–	–	–	–	2	–	260	990	1.0
Benzo[b]fluoranthene	0.1	5.0	73	–	–	–	–	–	–	–	2100	–	900
Benzo[k]fluoranthene	0.1	1.00	–	–	–	–	–	–	–	–	1500	–	–
Benzo[a]pyrene	1	20.0	–	–	–	–	–	2700	–	–	15,000	33,000	–
Indeno(1,2,3-c,d)pyrene	0.1	–	–	–	20	–	–	–	–	–	900	–	–
Dibenzo[a,h]anthracene	1	–	–	–	100	–	–	–	–	–	2000	–	–
Benzo[g,h,i]perylene	0.01	–	–	–	1.0	–	–	–	10	–	130	–	–
∑ (µg TEQ/k g)		29	1025	66	230	706	27	2700	247	56.12	23,738	46,699	924

^a TEF: Toxicity Equivalency Factor according to Nisbet and Lagoy.

4.3 Risk assessment of PAHs

Risk assessment can be evaluated by the incremental lifetime cancer risk (ILCR) associated with exposures to PAHs in plastic samples using the USEPA standard models (United State Environmental Protection Agency 1991, Chen and Liao 2006, Wang 2007). The cancer risk was assessed based on exposure over the entire lifetime. The ILCR (unitless) in terms of direct dermal contact is as follows: i = age interval; a = 0 ≤ 2 years, b = 2 ≤ 6 years, c = 6 ≤ 16 years, d = 16 ≤ 30 years. Where CS is the PAH concentration of plastic (mg/kg), CF is the conversion factor (kg mg⁻¹), AF is the dermal adherence factor (mg cm⁻²), ABS_d is the dermal adsorption fraction (unitless), EV is the event frequency (d⁻¹), SA is the dermal surface exposure (cm²/d), EF is the exposure frequency (d/year), ED is the exposure duration (year), SF_dermal is carcinogenic slope factor (mg/kg/d)⁻¹, ADAF_i is Age-dependent adjustment factor for age “i” (unitless), BW is body weight (kg), AT is the average life span (year), and ABS_GI is fraction of contaminant absorbed in gastrointestinal tract (unitless).

The determination of carcinogenic slope factor was based on the cancer-causing ability of Benzo[a]Pyrene; SF_Dermal of BaP was 25 (mg/kg/d)⁻¹ (United State Environmental Protection Agency 1994, Knafla et al. 2006, Wang 2007). The CS was obtained by converting concentrations of PAHs according to toxic equivalents of Benzo[a]Pyrene using the toxicity equivalency factor (TEF), and the sum was then obtained (Liao and Chiang 2006). Other body functions-related parameters were based on the Risk Assessment Guidance of PAHs in plastic and are shown in Table 6.

Table 6. Parameters used in the incremental lifetime cancer risk assessment (USEPA 1991, USEPA 2004).

		Age groups (Years)
Parameter	Units	0 ≤ 2	2 ≤ 6	6 ≤ 16	16 ≤ 30	Adult >30
Body weight (BW)	kg	15	15	70	70	90
Exposure frequency (EF)	d/year	350	350	350	350	350
Exposure duration (ED)	year	2	4	10	14	24
Dermal surface exposure (SA)	cm^2/d	2800	2800	5700	5700	5700
Dermal adherence factor (AF)	mg/cm	0.2	0.2	0.07	0.07	0.07
Dermal adsorption fraction (ABSd)	unitless	0.1	0.1	0.1	0.1	0.1
Gastrointestinal adsorption fraction (ABSGI)	unitless	1	1	1	1	1
Averaging life span (AT)	days	25,550	25,550	25,550	25,550	25,550
Age-dependent adjustment factor for age (ADAFi)	unitless	10	3	3	1	1
Conversion factor (CF)	kg/mg	1.0 × 10^−6	1.0 × 10^−6	1.0 × 10^−6	1.0 × 10^−6	1.0 × 10^−6

Table 7 shows the incremental lifetime cancer risks (ILCRs) from exposure to PAHs in carbon black-containing plastic parts of consumer products by dermal exposure pathway, to an individual exposed for 70 years, starting at birth using the USEPA (United State Environmental Protection Agency 1991, 2004) recommended standard default exposure parameters for a Reasonable Maximum Exposure (RME) resident.

Table 7. The incremental lifetime cancer risks (ILCRs) of exposing to carbon black-containing plastic parts of consumer products PAHs through dermal contacts.

Age interval (year)	Sample 1 (Gloves)	Sample 2 (Mouse pad)	Sample 3 (Car wiper)	Sample 4 (Rubber shoe)	Sample 5 (Bicycle grip)	Sample 6 (Toilet plunger)	Sample 7 (Car mat)	Sample 8 (Gas O-ring)	Sample 9 (Gas tube)	Sample 10 (Used car mat)	Sample 11 (Toy wheel)	Sample 12 (Electrical wire)
0–<2	8.79 × 10^−7	2.62 × 10^−5	3.92 × 10^−7	4.78 × 10^−6	1.79 × 10^−5	6.71 × 10^−7	6.84 × 10^−5	6.42 × 10^−6	1.44 × 10^−6	6.24 × 10^−4	1.18 × 10^−3	2.34 × 10^−5
2–<6	5.27 × 10^−7	1.57 × 10^−5	2.35 × 10^−7	2.87 × 10^−6	1.07 × 10^−5	4.03 × 10^−7	4.11 × 10^−5	3.85 × 10^−6	8.61 × 10^−7	3.75 × 10^−4	7.08 × 10^−4	1.40 × 10^−5
6–<16	2.01 × 10^−7	6.01 × 10^−6	8.98 × 10^−8	1.09 × 10^−6	4.10 × 10^−6	1.54 × 10^−7	1.57 × 10^−5	1.47 × 10^−6	3.29 × 10^−7	1.43 × 10^−4	2.70 × 10^−4	5.35 × 10^−6
16–<30	9.39 × 10^−8	2.80 × 10^−6	4.19 × 10^−8	5.11 × 10^−7	1.91 × 10^−6	7.18 × 10^−8	7.31 × 10^−6	6.86 × 10^−7	1.53 × 10^−7	6.67 × 10^−5	1.26 × 10^−4	2.50 × 10^−6
30–<70	1.25 × 10^−7	3.74 × 10^−6	5.59 × 10^−8	6.81 × 10^−7	2.55 × 10^−6	9.57 × 10^−8	9.75 × 10^−6	9.14 × 10^−7	2.05 × 10^−7	8.89 × 10^−5	1.68 × 10^−4	3.33 × 10^−6
ILCRsDermal	1.83 × 10^−6	5.45 × 10^−5	8.15 × 10^−7	9.93 × 10^−6	3.72 × 10^−5	1.40 × 10^−6	1.42 × 10^−4	1.33 × 10^−5	2.98 × 10^−6	1.30 × 10^−3	2.45 × 10^−3	4.86 × 10^−5
Theor. No of cancer cases	2	55	1	10	37	1	142	13	3	1300	2450	49

The total estimated cancer risk to the individual is the sum of the risks across all five age intervals.

5. Discussion

This study was performed to monitor the concentrations of PAHs in carbon black-containing plastic and rubber samples from the Jordanian market. It was possible to determine the concentrations of 13 PAHs in the studied samples.

The studied PAHs compounds were found in almost all samples. The total concentrations of the studied PAHs were ranged from 1.5 to 547 mg/kg (Table 4).

The highest total concentration of PAHs was found in toy wheel sample (547 mg/kg), this type of samples may not be contacted by hand for long time periods but there are some children who may put this part in their mouth, which increases the possibility to be exposed to PAHs, and having high levels of PAHs in this type is extremely danger.

The lowest total concentration of PAHs was found in gloves (1.5 mg/kg), which is favorable to have as much as low concentrations of PAHs as possible because human’s skin is highly exposed to gloves, during long periods of time and friction.

While comparing the results for the thirteen PAHs in the tested samples, we found that the concentration ranges for each analyte is as the following: Fluorene ranging from ND in car mat to 148 mg/kg in bicycle grip; Phenanthrene ranging from 0.20 mg/kg in car mat to 177 mg/kg in bicycle grip; Anthracene ranging from ND in car mat and electrical wire to 36 mg/kg in bicycle grip; Fluoranthene ranging from ND in car mat to 31 mg/kg in used car mat; Pyrene ranging from ND in car mat to 147 mg/kg in toy wheel; Benzo[a]anthracene ranging from 0.00 mg/kg in car wiper, rubber shoe, bicycle grip, toilet plunger, car mat, and gas tube to 124 mg/kg in toy wheel; Chrysene ranging from 0.00 mg/kg in gloves, car wiper, rubber shoe, bicycle grip, toilet plunger, car mat, and gas tube to 99 µg/g in toy wheel; Benzo[b]fluoranthene ranging from 0.00 mg/kg in car wiper, rubber shoe, bicycle grip, toilet plunger, car mat, gas O-ring, gas tube, and toy wheel to 21 mg/kg in used car mat; Benzo[k]fluoranthene ranging from 0.00 mg/kg in gloves, mouse pad, car wiper, rubber shoe, bicycle grip, toilet plunger, car mat, gas O-ring, gas tube, toy wheel, and electrical wire to 15 mg/kg in used car mat; Benzo[a]pyrene ranging from 0.00 mg/kg in gloves, mouse pad, car wiper, rubber shoe, bicycle grip, toilet plunger, gas O-ring, gas tube, and electrical wire to 33 mg/kg in toy wheel; Indeno (1,2,3-c,d) pyrene ranging from 0.00 mg/kg in gloves, mouse pad, car wiper, bicycle grip, toilet plunger, car mat, gas O-ring, gas tube, toy wheel, and electrical wire to 9 mg/kg in used car mat; Dibenzo[a,h]anthracene ranging from 0.00 mg/kg in gloves, mouse pad, car wiper, bicycle grip, toilet plunger, car mat, gas O-ring, gas tube, toy wheel, and electrical wire to 2 mg/kg in used car mat; and Benzo[g,h,i]perylene ranging from 0.00 mg/kg in gloves, mouse pad, car wiper, bicycle grip, toilet plunger, car mat, gas tube, toy wheel, and electrical wire to 13 mg/kg in used car mat.

Samples which have a high contact time are gloves, mouse pad, rubber shoe, and bicycle grip. The gloves show the highest concentrations of Pyrene (0.5 mg/kg), Phenanthrene (0.3 mg/kg), and Fluorene (0.29 mg/kg). The mouse pad shows the highest concentrations of Phenanthrene (99 mg/kg), Fluorene (67 mg/kg), and Fluoranthene (24 mg/kg). The rubber shoe shows the highest concentrations of Fluorene (12 mg/kg), Phenanthrene (6 mg/kg), and Anthracene (0.9 mg/kg). The bicycle grip shows the highest concentrations of Phenanthrene (177 mg/kg), Fluorene (148 mg/kg), and Anthracene (36 mg/kg). The car wiper shows the highest concentrations of Fluorene (6 mg/kg), Phenanthrene (3 mg/kg), and Pyrene (0.8 mg/kg). The toilet plunger shows the highest concentrations of Phenanthrene (7 mg/kg), Fluorene (7 mg/kg), and Fluoranthene (2 mg/kg). The car mat shows the highest concentrations of Benzo[a]pyrene (3 mg/kg) and Phenanthrene (0.20 mg/kg). The gas O-ring shows the highest concentrations of Phenanthrene (47 mg/kg), Fluorene (31 mg/kg), and Anthracene (12 mg/kg). The gas tube shows the highest concentrations of Phenanthrene (14 mg/kg), Fluorene (12 mg/kg), and Anthracene (3 mg/kg). The used car mat shows the highest concentrations of Fluoranthene (31 mg/kg), Pyrene (28.0 mg/kg), and Phenanthrene (27 mg/kg). The toy wheel shows the highest concentrations of Pyrene (147 mg/kg), Benzo[a]anthracene (124 mg/kg), and Chrysene (99 mg/kg). The electrical wire shows the highest concentrations of Benzo[b]fluoranthene (9 mg/kg), Phenanthrene (1.4 mg/kg), and Pyrene (1.2 mg/kg). All previous results are shown in Figure 1.

Figure 1. PAHs concentration in samples 1–6 (above) and 7–12 (below).

The highest total concentration was found in toy wheel (547 mg/kg) followed by bicycle grip (382 mg/kg) followed by mouse pad (235 mg/kg) followed by used car mat (221 mg/kg).

According to the criteria that was issued by the European commission (REACH), regarding the concentration of any PAHs in consumer articles that must be less than 1 mg/kg (1 ppm), which will be effective and applied starting from December 27 2015 (European Union 2013), it was found that all studied consumer articles are not compatible with this specification. All studied articles contain concentrations greater than 1 mg/kg for any of the PAHs, except the gloves sample which was found to contain less than 1 mg/kg of any of the PAHs. TEQ indicates that the article with the highest value is the most toxic (carcinogenic) one. The toy wheel having the highest total TEQ (46 699 ng TEQ/g) (Table 4) among all samples makes it the most carcinogenic one, and being used by children makes it so important to decrease this value as they may put the toy wheel in their mouth. The second highest TEQ concentration was found in the used car mat (23 738 ng TEQ/g), but this sample is not so dangerous to children as the toy wheel. The car wiper is the least carcinogenic sample, but it will not be of high importance as the car wiper is not contacting with skin for long time periods.

The total estimated cancer risks of exposure to PAHs in the samples were ranged from 8.15 × 10⁻⁷ in the car wiper to 1.30 × 10⁻³ in the used car mat (Table 7).

According to USEPA guideline in regulatory terms, an estimated cancer risk of 10⁻⁶ or less denotes virtual safety and an estimated cancer risk of greater than 10⁻⁴ denotes potentially high risk (Chen and Liao 2006). Hence, car wiper is the only sample which is virtually safe and car mat, used car mat and toy wheel are potentially high cancer risk samples.

By multiplying the estimated cancer risks of exposing (ILCRs) to PAHs in the samples by 10⁶, it is possible to determine the theoretical number of cancer cases per million of people. Therefore, the number of people who are suspected of cancer due to exposure to carbon black-containing plastic parts of consumer products out of million people is 2 for gloves, 55 for mouse pad, 1 for car wiper, 10 for rubber shoe, 37 for bicycle grip, 1 for toilet plunger, 142 for car mat, 13 for gas O-ring, 3 for gas tube, 1300 for used car mat, 2450 for toy wheel, and 49 for electrical wire.

Both the results of TEQ and those of the total estimated cancer risk show that the most dangerous and carcinogenic type of carbon-black containing plastic article is the toy wheel, and the least carcinogenic is the car wiper and toilet plunger samples.

4. Conclusion

This study was carried out to find the concentrations of PAHs, which are Persistent Organic Pollutant (POP) found in nature, in black rubber and plastic parts of consumer articles in the Jordanian market. This study is the first of its kind in Jordan.

The studied PAHs compounds were found in almost all samples. The total concentrations of the studied PAHs were ranged from 1.3 to 528 mg/kg.

According to the criteria that was issued by European commission regarding the concentration of PAHs in consumer articles to be less than 1 mg/kg (1 ppm), which will be effective and applied starting from December 27 2015, all the analyzed samples were containing concentrations of more than 1 mg/kg (European Union 2013).

Both the TEQ and ILCR calculations show that the toy wheel sample is the most dangerous and carcinogenic type of all studied samples.

Disclosure statement

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of this article.