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Presence of the heavy metal lead in samples of tobacco (Nicotiana tabaccum) snuff in Nigeria.

Introduction

Tobacco snuff is one of the varieties of tobacco products that are not smoked (smokeless tobacco). It consists of finely ground leaves of the tobacco plant (Nicotiana tabaccum), which is prepared into dry or moist forms, and is sometimes packaged in ready-to-use pouches. Dry snuff is usually sniffed or swallowed, whereas moist snuff is placed between the gum and the lips or cheek where it is slowly dissolved and absorbed. [1]

Tobacco snuff contains more than 19 known carcinogens and at least 30 metallic compounds comprising some heavy metals such as lead (Pb), chromium (Cr), nickel (Ni), cadmium (Cd), selenium (Se), and mercury (Hg). [2] Tobacco is a rich source of these heavy metals because they get preferentially absorbed by the leaves of tobacco during plant growth. [3]

Harmful effects on human health are associated with prolonged exposure to these heavy metals. [4] Lead poisoning results in the interference with a variety of body processes, and lead is toxic to many organs and tissues including the heart, bones, intestines, kidneys, and reproductive and nervous systems. [5,6] It is also unsafe in pregnancy. [7]

Symptoms of lead poisoning include abdominal pain, confusion, headache, anemia, irritability, kidney failure, and in severe cases seizures, coma, and death. [8-10] Children can inhale tobacco snuff indirectly from parent users or as it is being prepared leading to toxicity over a prolonged period. Lead is particularly toxic to children, causing potentially permanent learning and behavioral disorders. [11]

This study was specifically directed at evaluating the presence of the heavy metal lead in samples of tobacco (N. tabaccum) snuff in Nigeria.

Materials and Methods

Study location: The study was conducted at the Department of Pharmacy, Madonna University, Elele Campus, Rivers State, Nigeria, from January to July 2013. Materials/apparatus: Petri dish, digestion bottle, test tube, beaker, filter paper, separator funnel. Chemicals: De-ionized water, dilute 0.1-M nitric acid, distilled water, standard solution of lead. Equipment/instruments (atomic absorption spectrophotometer [AAS]): Electronic weighing balance (model 2610; Ohaus), centrifuge, atomic absorption spectrophotometer machine (SP 2900 model; Pye Unicam) [Figure 1].

Sample Collection

Thirty samples of tobacco snuff were obtained from five geopolitical areas in Nigeria. The date of purchase, name of manufacturer, method of preparation, and place of purchase were all noted. Different brands were collected from each area. Samples of the same brand were mixed together to obtain a representative sample. Brand names were not disclosed because of legal requirement. The breakdown of sample, geographical area, and type are shown in Table 1.

Sample Pretreatment

Two grams of the dry snuff sample was weighed using an electrical weighing balance for specific analysis and pretreated as per standard procedure for different metals. This was done for each of the 30 samples.

Wet Acid Digestion Method

A known quantity of sample (2.0 g) was transferred into a digestion bottle. The sample was wet digested with 50 mL dilute nitric acid. This enhances the extraction of the metals in the tobacco snuff. The oven was set at a temperature of 110[degrees]C. The digested sample was kept in the oven for 2 h.

After removal from the oven, the digested sample was filtered using a filter paper to ensure that the residue obtained after digestion is free from organic matter, which otherwise acts as impurities during the metal analysis.

After filtration, the filtrate was further analyzed using AAS.

Sample Analysis

The filtrate obtained was further analyzed to detect the concentration of heavy metals using AAS. This is sensitive for the determination of heavy metals at low concentrations. It is based on the fact of absorption of radiation of definite wavelength characteristic of the element. Its high sensitivity is exemplified by the fact that most metals can be determined at the part per million and part per billion concentration level.

Atomic Absorption Spectroscopy

Atomic absorption spectroscopy is used principally in limit test for metals in drugs before their incorporation into formulation. The sample is generally dissolved in 0.1 M nitric acid to avoid formation of metal hydroxides from heavy metals, which are relatively volatile and suppress the AAS reading.

In atomic absorption spectroscopy, the metal atoms are volatilized in a flame and radiation is passed through the flame. The volatized atoms that are mainly in their ground state and not emitting energy will absorb radiation with an energy corresponding to the difference between their ground state and excited state.

Instrumentation of AAS

An AAS consists of the following components that enable effective analysis of heavy metals:

(a) Light source: This is made up of a hollow cathode lamp coated with the element being analyzed.

(b) Flame: This is usually air/acetylene providing a temperature of 250[degrees]C; nitrous oxides/acetylene may be used to produce temperatures up to 300[degrees]C, which are required to volatilize salts of elements such as aluminum or calcium.

(c) Monochromator. This is used to narrow down the width of the band of radiation being examined and is thus set to monitor the wavelength being emitted by the hollow cathode lamp. This cuts out interference by radiation emitted from the flame from the filter gas in the hollow cathode lamp and from other elements in the sample.

(d) Detector. This is a photosensitive cell.

Data Analysis

Daily Intake

The daily intake was calculated using the following equation of Dhaware et al. [9]:

DI ([micro]g/day) = [C.sub.metal] * [W.sub.analyses] * [D.sub.intake]

where [C.sub.metal] is the metal concentration in tobacco snuff sample (TSS) taken for analysis (in [micro]g/g), [W.sub.analyses] are the weight of TSS taken for analysis (2.0 g in this study), and [D.sub.intake] is the daily intake (assuming 10 pouches per day, 5.0 g/pouch).

Target Hazard Quotient

For the assessment of health risks arising from the indirect intake of heavy metals through the consumption of TSSs, target hazard quotient (THQ) was calculated in accordance to the methodology described by the USEPA. [12] Target Hazard Quotient is one of the methods of estimating risks based on the noncarcinogenic effects of the toxicant and the reference dose. [4] THQ was determined based on the formula (modified) given by Chien et al. [4]:

THQ = (EFr x [ED.sub.tot] TSIR x C/Rf[D.sub.o] x [BW.sub.a] x [AT.sub.n]) x [10.sup.-3]

where EFr is the exposure frequency = 312 days/year, equivalent to average lifetime; TSIR is the tobacco snuff ingestion rate = 50.0 g/day, equivalent to 10 pouches/day, 50.0 [micro]g/pouch of TSS; C is the concentration of metal in TSS in [micro]g/g; [RfD.sub.o] is the oral reference dose in mg/kg/day; [BW.sub.a] is the average body weight, adult = 60 kg; [AT.sub.n] is the average exposure time for noncarcinogens in days (EFr(312 days/ year) x [ED.sub.tot] (number of exposure years, assuming 70 years in this study); and [10.sup.-3] is the unit of conversion.

Result

Table 2 shows the comparison of concentration of lead in each sample collected from the four geopolitical zones of purchase. The daily intakes based on the different geographical areas from the table show variation in lead concentration. Southwest region shows the highest mean lead concentration in snuff samples, followed by north central, southeast. Northwest shows the least concentration of lead. This difference in mean lead concentration in the four zones is statistically significant (p < 0.05).

Table 3 shows the levels of the metal intake through the daily consumption of various TSSs and the percentage Food and Agricultural Organization/World Health Organization (FAO/WHO) violation. The daily intakes were calculated based on the consumption of 10 pouches per day. The various daily concentrations of lead in each of the samples were compared to that of the FAO/WHO standard, which is 5 [micro]g/kg/day. The table shows that all the TSSs exceeded the permissible limit by the WHO except for TSSs 21, 24, 25, 26, and 27, which had concentrations of lead below the permissible limit stipulated by the FAO/WHO.

Table 4 gives the daily intake of the assayed metal, compared with the provisional tolerable weekly intake and the proposed maximum permissible level suggested by the FAO/WHO.

Table 5 shows the results of THQ calculations to assess the potential health risk in the consumption of the TSSs. These THQs were calculated using the oral reference doses (mg/kg/day) (Pb-1.5) of the metal as stipulated by the United State Environmental Protection Agency (USEPA). [12]

The mean concentration of lead from the chart shows that the foreign made products had higher concentration of lead when compared to the Nigerian or locally made products [Figure 2].

Ethical Concentration

Permission was obtained from the ethics and research committee of Madonna University, Elele Campus, Rivers State, Nigeria, before the study was conducted.

Discussion

The study showed that the levels of lead in 27 of the 30 samples exceeded the daily recommended limit of 5 [micro]g/day set by the FAO/WHO. [13] Thus, a continuous intake of snuff could lead to bioaccumulation of this heavy metal, with the resulting negative health implications.

With respect to the individual percentage violation limit, all the samples except samples 21 and 24-27 exceeded the FAO/ WHO violation limit. The concentration of lead in the TSSs in Nigeria ranged from 0.41 to 1.13 [micro]g/g for north central, 0.45 to 2.48 [micro]g/g for southwest, 0.01 to 1.48 [micro]g/g for southeast, and 0.02 to 1.16 for northwest. This showed that the highest concentration of the heavy metal lead was found in the samples obtained from southwest Nigeria (0.45-2.48 [micro]g/g).

Lagos, Ibadan, and Sango Otta, which are some of the major industrial hub of the country, lie in the southwest Nigeria. A lot of land pollution from industrial waste and effluents released by paint, cement, cosmetic, and other factories may have been the reason for this. Heavy metals in the polluted soils are easily absorbed and retained by the leaves of N. tabaccum. [3] Incidentally, the Nigeria Tobacco company, the major producer of tobacco products in Nigeria, is located in the southwest.

The THQ for each of the sample was less than 1 (<1.0), which makes them nonhazardous as per the USEPA. [12] However, the level of lead violated the permissible levels of the FAO/WHO. Cumulatively, the THQ might be exceeded considering the fact that tobacco snuff is used chronically, thus leading to adverse effects on health. [14]

The study also showed that all the foreign TSSs (1,2, 12, 13, 15, 16, and 18) exceeded violation limit for lead recommended by the FAO/WHO, in contrast to some of the locally produced TSSs (20, 22, and 23-27), which did not exceed the violation limit. This showed that foreign tobacco snuffs were more contaminated with lead and indeed other heavy metals than the locally made snuffs. Foreign countries are more industrialized than Nigeria, hence the tendency for their soils to be more heavily contaminated with chemical pollutants, which are then absorbed by the leaves of tobacco plant in the farms. [14]

Also, crop farmers in foreign countries have more access to fertilizers and pesticides than Nigeria farmers, hence the tendency for their tobacco plants to be exposed more easily to lead and other heavy metals that are thereafter retained in the leaves, which will undergo eventual processing to snuff and other tobacco product. [14,15]

Conclusion

The study showed varying levels of the heavy metal lead in different brands of tobacco snuff obtained from various geopolitical zones of Nigeria. This evaluation shows that the majority of the tobacco snuffs in Nigeria is highly contaminated with lead and therefore constitutes major health risk to the local population. It also showed that foreign tobacco snuffs have a relatively higher concentration of lead than the local ones. This means a more profound adverse health effects on our population as our people often seem to prefer foreign goods to the locally made ones, including snuff.

Recommendation

The Federal Ministry of Health (FMOH) should regulate further with a stricter measure the production and use of all tobacco products in Nigeria. Also, health-care workers should enlighten their patients and the general populace on the obvious dangers inherent in the use of tobacco snuffs.

Acknowledgment

We thank Miss Onyejiaka Chinaza Vivian for the contribution to this manuscript and pharmacist (Mrs.) Zelinjo Igweze for supervising the work.

References

[1.] Peto R, Lopez AD, Boreham J, Thun MJ. Mortality from Smoking in Developed Countries, 1950-2000: Indirect Estimates from National Vital Statistics. New York: Oxford University Press, 2006. pp. 123-125.

[2.] Golia E, Dimirkou EA, Mitsios EIK. Accumulation of metals on tobacco leaves grown in an agricultural areas in relation to soil. Bull Environ Contam Toxicol 2007;79:158-62.

[3.] Stephen WF, Calder A, Newton J. Source and health implications of high toxic metal concentration in illicit tobacco products. Environ Sci Technol 2005;39:479-88.

[4.] Chien CL, Hung TC, Choang KY, Yel CY, Meng RJ, Shieh MJ, et al. Daily intake of TBT, Cu, Zn, Cd and As for fishermen in Taiwan. Sci Total Environ 2002;285:177-85.

[5.] Nevin R. How lead exposure relates to temporal changes in IQ, violent crime and unwed pregnancy. Environ Res 2000; 83(1):1-22.

[6.] Casarett LJ, Klaassen CD, Doull J. Toxic effect of metals. In: Casarett and Doull's Toxicology: The Basic Science of Poisons, Vol. 1. Pittsburgh, PA: McGraw-Hill, 2007.pp. 1-4.

[7.] Cleveland LM, Minter ML, Cobb KA, Scott AA, German VF. Lead hazards for pregnant women and children: part 2: more can still be done to reduce the chance of exposure to lead in at-risk populations. Am J Nurs 2008;108(10):40-9.

[8.] Cecil KM, Brubakar CS, Adlere CM, Dietrich KN, Altaye M, Egelhoff JC, et al. Decreased brain volume in adults with childhood lead exposure. Rev Environ Health 2008;5:e112.

[9.] Dhaware D, Deshpande A, Khandelar RN, Chowgule R. Determinants of toxic metals in Indian smokeless tobacco products. Scientific World Journal 2009;9:1140-7.

[10.] Hostynek JJ. Lead, manganese and mercury: metals in personal-care products. Cosmetics Toiletries Magazine 2001;116: 468-77.

[11.] Woolf AD, Goldman RJ, Bellinger DC. Update on the clinical management of childhood lead poisoning. Pediatr Clin North Am 2007;54(2):271-94.

[12.] USEPA. Risk based Concentration Table. Philadelphia, PA: United State Environmental Protection Agency, 2000.

[13.] United States Department of Human and Health Services. Toxicological Profile for Lead. Atlanta, GA: US Department of Human and Health Services, Public Health Services, Agency for Toxic substances, 2007.

[14.] Zulfigar S, Shabbir S, Isha M, Shaukat MS, Sarwar MI. Metal distribution in Pakistan and foreign brands of cigarette ash. Bull Environ Contam Toxicol 2006;77:679-86.

[15.] Asta J, Guillard E, Tissut M, Gaude T, Ravanel P. Heavy metal transfer from atmosphere to plants. J Phys 2003;107:65-7.

Source of Support: Nil, Conflict of Interest: None declared.

Prosper O Adogu (1), Joseph C Enye (2), Henry N Chineke (3), Irene A Merenu (3), Nonye B Egenti (4), Ifeoma A Modebe (1)

(1) Department of Community Medicine and PHC Nnamdi Azikiwe University Teaching Hospital/Nnamdi Azikiwe University, (NAU/NAUTH) Nnewi, Nigeria.

(2) Department of Pharmacy Madonna University Elele River State Nigeria.

(3) Department of Community Medicine Imo State University Owerri Nigeria.

(4) Department of Community Medicine, University of Abuja, Nigeria.

Correspondence to: Prosper O Adogu, E-mail: prosuperhealth50@gmail.com

Received May 20, 2015. Accepted May 28, 2015

DOI: 10.5455/ijmsph.2015.20052015272

Table 1: Breakdown of sample geographical area

Sample   Geographical    Town
         area

1        North central   Babangida Market, Suleja
2        North central   Babangida Market, Suleja
3        North central   Kuje Market, Abuja
4        Southwest       Iseyin Market, Oyo
5        Southwest       Iseyin Market, Oyo
6        Southwest       Iseyin Market, Oyo
7        Southwest       Iseyin Market, Oyo
8        Southwest       Agbeni Market, Ibadan
9        Southwest       Agbeni Market, Ibadan
10       Southwest       Illeshiro Market, Ibadan
11       Southwest       Illeshiro Market, Ibadan
12       Southeast       Main Market Onitsha
13       Southeast       Main Market Onitsha
14       Southeast       Main Market Onitsha
15       Southeast       Main Market Onitsha

16       Southeast       Main Market Onitsha
17       Southeast       Main Market Onitsha
18       Southeast       Main Market Onitsha
19       Southeast       Main Market Onitsha
20       Northwest       Aitiken Road, Sabon Gari Kano
21       Northwest       Yoruba Road, Sabon Gari Kano
22       Northwest       Yoruba road, Sabon Gari Kano
23       Southeast       Ochanga Market, Onitsha
24       Southeast       Ochanga Market, Onitsha
25       Southeast       Ahia Ohuru Market, Aba
26       Southeast       Ahia Ohuru Market, Aba
27       Southeast       Umuahia Market
28       Southeast       Umuahia Market
29       Southeast       King's Palace, Aba
30       Southeast       King's Palace, Aba

Sample   Type/name

1        Foreign snuff
2        Medicated
3        Local
4        Local
5        Local
6        Local
7        Local
8        Local
9        Local
10       Local
11       Local
12       UAC & Campbell foreign
13       Foreign
14       Local
15       Campbell, KTC, &
           Maxwell (foreign)
16       KTC (foreign)
17       Broken (local)
18       Medicated
19       Maxwell (foreign)
20       Local
21       Local
22       Medicated
23       Medicated
24       Local
25       Local
26       Medicated
27       Local
28       Broken
29       Local
30       Medicated

Table 2: Concentrations of lead in each of the tobacco snuff
samples by geopolitical zone

Geopolitical    Sample       Lead       Mean [+ or -] SD
zone                     ([micro]g/g)

North central   TSS 1       1.4125        1.013 + 0.4
                TSS 2       1.0612
                TSS 3       0.4536
                TSS 4       1.1252
Southwest       TSS 5       0.6349        1.11 + 0.69
                TSS 6       1.0882
                TSS 7       0.4536
                TSS 8       1.1720
                TSS 9       0.5974
                TSS 10      2.4770
                TSS 11      1.3421
Southeast       TSS 12      0.6942        0.58 + 0.52
                TSS 13      0.4893
                TSS 14      1.2571
                TSS 15      0.6529
                TSS 16      1.3694
                TSS 17      0.7241
                TSS 18      0.5059
                TSS 19      1.0972
                TSS 23      0.8053
                TSS 24      0.0291
                TSS 25      0.0072
                TSS 26      0.0121
                TSS 27      0.0049
                TSS 28      0.1171
                TSS 29      0.0692
                TSS 30      1.4836
Northeast       TSS 20      1.1610         0.43 + 0.4
                TSS 21      0.0219
                TSS 22      0.1067

Geopolitical    Sample   F-test/p-value
zone

North central   TSS 1       F = 2.91
                TSS 2       p < 0.05
                TSS 3
                TSS 4
Southwest       TSS 5
                TSS 6
                TSS 7
                TSS 8
                TSS 9
                TSS 10
                TSS 11
Southeast       TSS 12
                TSS 13
                TSS 14
                TSS 15
                TSS 16
                TSS 17
                TSS 18
                TSS 19
                TSS 23
                TSS 24
                TSS 25
                TSS 26
                TSS 27
                TSS 28
                TSS 29
                TSS 30
Northeast       TSS 20
                TSS 21
                TSS 22

Table 3: Daily intake and percentage violation of each TSS from
the WHO/FAO standard

Sample   Pb ([micro]g/     Percentage
            kg/day)        violation
                            from the
                            WHO/FAO
                            standard
                         (@ 5 [micro]g/
                            kg/day)

TSS 1        141.0            2820
TSS 2        106.0            2120
TSS 3         45.0             900
TSS 4        113.0            2260
TSS 5         63.0            1260
TSS 6        109.0            2180
TSS 7         45.0             900
TSS 8        117.0            2340
TSS 9         60.0            1200
TSS 10       248.0            4960
TSS 11       134.0            2680
TSS 12        69.0            1380
TSS 13        49.0             980
TSS 14       126.0            2520
TSS 15        65.0            1300
TSS 16       137.0            2740
TSS 17        72.0            1440
TSS 18        51.0            1020
TSS 19       110.0            2200
TSS 20       116.0            2320
TSS 21         2.0              40
TSS 22        11.0             220
TSS 23        81.0            1620
TSS 24         3.0              60
TSS 25         1.0              20
TSS 26         1.0              20
TSS 27         0.5              10
TSS 28        12.0             240
TSS 29         7.0             140
TSS 30       148.0            2960

Table 4: Permissible intake levels as per the FAO/WHO
recommendations

Metal    Provisional     Per day      For a 60-kg     Reference
          tolerable       intake       individual
        weekly intake   ([micro]g/   ([micro]g/day)
         ([micro]g/      kg/day)
          kg/week)

Pb          25.0           5.0           300.0         FAO/WHO

Table 5: Target hazard quotient for lead from consumption of TSSs

TSS               Frequency    THQ

1, 16                 2       0.0008
2, 4, 6, 19, 20       5       0.0006
3, 7, 9, 13, 18       5       0.0003
5, 12, 15, 17         4       0.0004
8, 11, 14             3       0.0007
10                    1       0.0014
21,24-27, 29          6       0.0000
22, 28                2       0.0001
23                    1       0.0005
30                    1       0.2167

Figure 2: Daily mean concentration of lead ([mu]g/kg/day) in Nigerian
and foreign TSSs.

Tobacco snuff sample type

Nigerian    74.3
Foeign      75.2

Note: Table made from bar graph.
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Title Annotation:Research Article
Author:Adogu, Prosper O.; Enye, Joseph C.; Chineke, Henry N.; Merenu, Irene A.; Egenti, Nonye B.; Modebe, I
Publication:International Journal of Medical Science and Public Health
Article Type:Report
Date:Sep 1, 2015
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