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Vol. 7(8), pp. 291-301, August, 2013
DOI: 10.5897/AJPAC2013.0501
ISSN 1996 - 0840 © 2013 Academic Journals
http://www.academicjournals.org/AJPAC
African Journal of Pure and Applied
Chemistry
Full Length Research Paper
Analysis of the levels of arsenic in home-made brews,
spirits, in water and raw materials using Hgaas in
Nairobi county
Masime Jeremiah O*, Wanjau Ruth, Murungi Jane and Onindo Charles
Department of Chemistry, Faculty of Science, Kenyatta University, Nairobi, Kenya.
Accepted 1 August 2013
This study was carried out to determine the levels of arsenic in the home-made brews, home-made
spirits, raw materials and water. One hundred and thirty two home - made alcoholic beverages, one
hundred and ten water and eighteen raw materials samples obtained from various parts of Nairobi
slums and its environs were analyzed for arsenic. The method of analysis was hydride generation
atomic absorption spectroscopy. All home-made brews samples contained concentrations of arsenic
that were lower than the standard for total arsenic allowed in water. The concentrations of arsenic in
both brew and water ranged from ND to 0.88 ± 0.028 mg/L. These concentrations in these homemade
brews and raw materials used varied depending on the brew. The recommended maximum
contamination levels set by Kenya Bureau of Standards (KEBS) and WHO for arsenic in alcohols is 0.05
mg/L. Values of arsenic obtained in the drinks and the raw materials used were generally low. This also
implies that the tap water and home-made brews are safe. In general, those consuming home-made
brews are the young and elderly living in the slum areas in Nairobi County and it is these populations
that is more vulnerable to over exposure of this metal. It is recommended that foods and drinks be
tested for arsenic regularly to determine whether they meet the EPA/WHO standards.
Key words: arsenic, HGAAS, homemade brews.
INTRODUCTION
Arsenic
Arsenic occurs naturally in ground water in the form of
inorganic arsenates (As (III) and arsenate (As (v))
dissolved from rock. It is ranked 20
th
among the elements
in abundance in the earths crust. The toxicity
characteristics will vary with the different ions of arsenic
(Chasteen, 2009). Its abundance in the continental crust
of the earth is generally given as 1.5 to 2 mg/g; making it
relatively scarce (Chasteen, 2009). Arsenic exposure is
natural but can be aggravated by human activities. We
are exposed to arsenic in two chemical forms (The
University of Arozona, 2013):
(1) Inorganic – Varying amounts of this poisonous (toxic
forms) form can be found in:
(2) Organic – (arsenic compounds that contain carbon) –
varying amounts of this non-poisonous (low-toxicity) form
are found in the University of Arozona (2013):
(i) Animals
(ii) Plants
(iii) Fish and seafood
Arsenic is mainly transported into the environment by
water. The total amount of arsenic in the human blood
has been estimated to be between 15 to 20 µg/L but
*Corresponding author. E-mail: masimejo@yahoo.com.
292 Afr. J. Pure Appl. Chem.
concentrations of between 0.8 to 2.4 mg/L are toxic
(Chasteen, 2009). Surface water can be contaminated by
contact with soils, sediments and mine tailings (large
piles of crushed rock left over after minerals have been
extracted from the rocks which contained them) that
contain arsenic, runoff and wastewaters contaminated
with arsenic, arsenic-containing pesticides and industrial
wastes (The University of Arozona, 2013).
Most foods contain low levels of arsenic. Fish, seafood,
algae and rice can contain elevated levels of organic
forms of arsenic, however these forms of arsenic have
much lower toxicities than inorganic forms (The
University of Arozona, 2013).
A WHO task group has estimated that a lifetime
exposure to arsenic in drinking water at a concentration
of 0.2 mg/L gave a 5% risk of getting skin cancer
(Chasteen, 2009). It also causes inflammation, skin
lesions and neurological effects (Chasteen, 2009). The
arsenic levels in food regulations prescribe a maximum of
0.01 mg/L for water (Chasteen, 2009). Sources of arsenic
in environmental pollution include; burning of wood
treated with arsenic, use of geothermal energy, fertilizer,
herbicides, fungicides, formation of arsine whenever
hydrogen is being evolved in any step of an industrial
process, such as manufacture of paints, dyes,
insecticides, drugs and felt hats and curing hide,
fumigation of buildings and treatment of electricity poles
(Chasteen, 2009).
Health effects of arsenic to humanity
Most of the toxic effects arise from exposure to inorganic
arsenic and affects nearly all organ systems of the body.
Arsenic is known to cause cancer in humans (human
carcinogen). Ingested inorganic arsenic increases a
person’s risk to develop lung, skin, bladder, breast,
prostate, kidney and liver cancer. Other toxic effects of
concern are related to:
(a) Heart and blood vessels (cardiovascular)
(b) Stomach and intestines (gastrointestinal)
(c) Kidney effects
(d) Liver
(e) Nerves and nervous system (neurological)
(f) Lungs (pulmonary)
(g) Child birth (reproductive)
(h) Respiratory
(i) Blood & blood forming organs (hematology)
(j) Dermal (skin)
Chronic exposure to arsenic levels over 10.0 parts per
billion (ppb) has been linked to health complications,
including cancer of the skin, kidneys, lung and bladder,
as well as other diseases of the skin, neurological and
cardiovascular systems (Garness, 2007). Health
problems related to the intake of drinking water
containing high concentrations of arsenic have been
encountered in some regions of Taiwan, Argentina, and
Chile mainly in areas of volcanic activities (Chasteen,
2009). In 1999, the National academy of Science found
out that drinking water polluted with arsenic caused
bladder, lung, skin, liver and kidney cancers. Ingestion of
inorganic arsenic also led to nasal and prostate cancer
(USEPA, 2001). The arsenic poisoning is a tragic and
unforeseen consequence of good intentions.
Maximum limits of Arsenic allowed in food and
beverages
The WHO permissible limit of Arsenic for drinking water is
0.01 mg/L and the FAO permissible limit of Arsenic
for irrigation water is 0.10 mg/L (Wijesekara and
Marambe, 2011). For certain regions of the world where
concentrations of inorganic arsenic in drinking water
exceed 50 to 100 μg/L, some epidemiological studies provide
evidence of adverse effects (WHO, 2011; the WHO
guideline value of Arsenic in drinking water is 10 μg/L)
(Wijesekara and Marambe, 2011). However, in other
areas where arsenic concentrations in water are elevated
but are less than 50 μg/L, though there is a possibility
that adverse effects could occur as a result of exposure
to inorganic arsenic from water and food, according to
WHO (2011) and Wijesekara and Marambe (2011).
these would be at a low incidence that would be difficult
to detect in epidemiological studies. China have established
maximum limits for total Arsenic in many foods, including 0.01 mg/L
for drinking water, 0.5 mg/kg for raw cereals and/or cereal- based
foods (except rice and rice-based products), vegetables,
edible fugues, meat and its products, sugar, condiments,
milk powder, coca and its products included in
chocolates, and 0.1 mg/kg for the oil and fats as well as
raw milk. China has also established the maximum limits for
inorganic arsenic in rice and rice-based products (0.2 mg/kg),
fish and fish-based condiments (0.1 mg/kg), other sea
food and seafood-based condiments (0.5 mg/kg), cereal-
based infant f or m ula (0 . 2 m g / k g) , a n d
se a w e e d - b a se d in f a nt f o rm u l a (0. 3
m g/k g ) (Wijesekara and Marambe, 2011).
Status of arsenic contamination in Asia
Concentrations of Arsenic in unpolluted surface water
and groundwater are typically in the range of 1 to 10
µg/L, and elevated concentrations in surface water and
groundwater of up to 100 to 5000 µg/L can be found in areas of
sulfide mineralization (Wijesekara and Marambe, 2011).
El e v a t ed concentrations (> 1 mg Arsenic/L) in groundwater of
geochemical origins have been found in Taiwan (Wijesekara
and Marambe, 2011), West Bengal, India (Wijesekara and
Marambe, 2011). Das Levels as high as 35 mg Arsenic/L
and 25.7 mg Arsenic/L have been reported in areas
associated with hydrothermal activity (Wijesekara and
Marambe, 2011). Reported levels of total arsenic in
rice are < 0.01 to 2.05 mg/kg for Bangladesh,
0.31 to 0.70 mg/kg for China and < 0.10 to 0.76
mg/kg for Taiwan, 0.03 to 0.044 mg/kg for India, 0.11 to
0.66 mg/kg for the U.S.A., 0.03 to 0.47 mg/kg for Vietnam, and 0.08
to 0.38 mg/kg for Italy and Spain (Wijesekara and
Marambe, 2011).
Raw materials for home brewed alcoholic beverages
and spirits in East Africa
If a starchy food grain is fermented, it produces enzymes,
which start to break the starch down into sugar. This is
how growing plants derive energy; and this is how people
release sugar from grains so that they can make alcohol
from them, by brewing the grains into beer. In the
nineteenth century, brewing was the usual process of
making alcoholic beverages in most parts of East Africa;
mostly the grain used was finger millet (elevisine) but
some people used sorghum. Busaa is prepared from
cereals, chang’aa is a distilled brew consumed in most
parts of Kenya (Alcohol in East Africa, 2000). They are
made from a variety of grains - malted millet and malted
maize being the most common. It has a pleasant sweet
flavour and contains at least 50% alcohol (Alcohol in East
Africa, 2000); miti is prepared from boiled roots and
honey, while muratina is prepared from sugarcane or
honey, which is fermented using sausage plant (Kigelia
african). The conditions and raw materials used to
prepare these homemade brews/spirits may introduce
toxic materials into the alcohols and hence the need for
continuous monitoring of the levels of nutrients in the
alcohols to make sure that the population is not exposed
to dangerous levels.
In the twentieth century, maize has become a common
ingredient in the making of alcoholic brews (Alcohol in
East Africa, 2000). There are many other raw materials
as well, which include bananas, coconuts, palm fluid,
honey, pineapples, paw paws and many other fruits.
Some of the techniques used are by no means new.
Other techniques like those for distilled brews are new.
Brewing from grain takes several days. In most cases
there is no attempt to control the yeast other than the
constant reuse of the same containers for brewing. Once
brewed, the beer lasts for only a day or two; as a ‘live’
brew, spoils quickly, and if not drunk within about forty-
eight hours it will be spoiled. Nor can it be transported
any great distance, for the continuing fermentation
produces gases, which make it impossible to seal the
beer in a container (Alcohol in East Africa, 2000).
Arsenic in plants
From other researchers, the highest concentration of
Jeremiah et al. 293
arsenic was found in plant roots, the intermediate level in
vegetative tissues (leaves and stems), and the lowest
level in reproductive tissue (fruits and seeds)
(Chomkamon et al., 2013). Plants absorb arsenic fairly
easily, so that high-ranking concentration may be
present. Among many of public researches, most studies
had focused on foods and not much on the information
that was available on plants especially in the part of
rhizomes although it was a high opportunity for arsenic
accumulation (Chomkamon et al., 2013). The level of this
metal in the environment and in foods needs to be
monitored consistently. The goal of this study is to
determine the arsenic levels in home-made brews, tap
water and the raw materials used using UV – visible
Spectroscopy in the Nairobi County.
MATERIALS AND METHODS
Samples and sampling
Eleven stations were targeted and ten samples of each brew and
water were selected. A total of one hundred and fifty three home-
made alcoholic beverages, thirty three water and eighteen raw
materials samples were analyzed for arsenic. Samples of maize,
millet, sorghum, honey, jaggery and muratina were selected. Three
samples of each were obtained from various places in the eleven
stations. These samples were randomly obtained from various parts
of Nairobi County taking into account the requirements for the
preparation of the brews (Figure 1). This information was obtained
from the people who sold the brews. Sample of raw materials were
obtained from market places nearest to the beverage sampling
stations. A 100 ml samples were collected directly into specially
cleaned, pretested, polypropylene bottles using sample handling
techniques specially designed for collection of sample for the
analysis of metals at trace levels. The samples were then either
laboratory preserved by the addition of 5 ml of pretested 10% HNO
3
per litre of sample, depending on the time between sample
collection and arrival at the laboratory.
Reagents, chemicals, solvents, standards and blanks
Arsenic standard
The analyst 800 auto sampler was used to prepare a calibration
curve of 5, 10 and 15 µg/L from the 10 µg/l arsenic standard. A QC
standard was also measured by this method, high purity standards
TM-A, (Charleston, SC 29423) and was certified to be 15 µg/L
arsenic (Davidowski and Sarojam, 1990). A volume of 1.0 ml
arsenic stock solution was pipetted into a 1 L volumetric flask and
brought to volume with reagent water containing 1.5% concentrated
HNO
3
depending on the original concentrations of arsenic in the
sample (Delgado et al., 2003). Then 10.0 ml of the primary dilution
arsenic was pipetted into a 100 ml volumetric flask and brought to
volume with reagent water containing 1.5% concentrated HNO
3
/L (1
ml = 0.01 µg As).
Instruments and apparatus
All the weighing were done using a research analytical balance
(Sartorious research, R 200D, model-40110044, Analos, Belgium).
Other apparatus included the following; graduated pipettes (10 and
294 Afr. J. Pure Appl. Chem.
Figure 1. The map of Nairobi County.
5 ml), micropipettes (200 ml) and tips, test tubes (13 × 100 ml),
small square of parafilm, volumetric flasks (50 and 100 ml) and
computer.
HGAAS instruments
The arsenic concentrations were read on a Varian SpectrAA-40
atomic absorption spectrophotometer in conjunction with varian
VGA-76 hydride generator and absorption cell (Hawthorn, 2011).
Cleaning of apparatus
Cleaning of apparatus was adopted from Mendham et al. (2002),
and AOAC (2000) (William, 2000). Research apparatus as
recommended by Association of Official Analytical Chemists
(AOAC) were used. Sampler check blanks were generated in the
laboratory or of the equipment cleaning contractor’s facility by
processing reagent water through the sampling devices using the
same procedure sampling that is, bottles were cleaned with liquid
detergent and thoroughly rinsed with reagent water. The bottles
were then immersed in a hot (50 to 60°C) bath of 1 N trace metal
grade HCl for at least 48 h. The bottle were then thoroughly rinsed
with reagent water and filled with 0.1% (v/v) ultra pure HCl and
double-bagged in new polyethylene zip-type bags until needed
(USEPAOW, 1996). The apparatus were cleansed using
detergents, water, rinsed with distilled deionized water and dried
overnight in the oven at 100°C.
Sample collection and pretreatment
Water
All the water sample bottles were first rinsed with water before the
samples were collected. Preservation of water samples was
performed in the field or in the laboratory. Laboratory preservation
of water samples were done to expedite field operations and to
minimize the potential for sample decomposition. Water samples
and field blanks were then preserved in the laboratory immediately
when received. Preservation involved the addition of 10% HNO
3
to
bring the sample to pH < 2. For samples received at neutral pH,
approximately 5 ml of 10% HNO
3
per litre was required (William,
2000). These were stored in a refrigerator at below 4°C to avoid
further fermentation.
Brews
The brew sample bottle (acid-washed, 125 ml polyethene bottle)
were rinsed 3 times before sampling. Filled to approximately 2/3
full, tighten cap and freeze cruise, cast Niskin bottle number were
recorded on the bottle and data sheet. All the brew sample bottles
were first rinsed with the alcohol for alcohol samples before the
brew samples were collected. The samples were then filtered, the
residue discarded and the filtrates from home made brews were
decolorized using activated charcoal and re-filtered until the colour
disappeared.
Raw materials
In the sample pretreatment, modified procedures for washing and
drying proposed by Santos et al. (2004) and Kawashima and
Soares (2003). respectively, were used. First, each raw material
samples were first rinsed with distilled water to remove dirt and
other debris. Then the raw material samples were brushed with
polypropylene bristles and washed with deionized water. The raw
materials were then grated with a polypropylene grater into
porcelain containers. Then the containers with the raw material
samples were dried in a laboratory oven at 65 ± 5°C for 24 h or until
Jeremiah et al. 295
Table 1. Microwave digestion program.
Step
Power
Ramp (min)
Hold (min)
Fan speed
1
750
10
10
1
2
1200
10
10
1
3
0 (cool Down)
0
15
3
reaching constant weight. Immediately afterwards, the samples
were stocked in polypropylene beakers and covered with a
Polyvinyl chloride (PVC) film. Finally, they were stored in a
desiccators awaiting digestion (Rodrigo et al., 2011).
Sample preparation
Sample preparation for arsenic analysis
In the hydride generation for the analysis of arsenic, the hydride
generator was set up according to the Varian Instruction Manual.
Pumping rates were checked and adjusted to between 5
and 7 ml
for the sample tube and between 0.8
and 1.0 ml
for the reagent
tubes (hydrochloric acid 75% and sodium borohydride 0.6%
respectively (Hawthorn, 2011).
Sodium tetrahydroborate solution was prepared by weighing
between 2 and 20 g of its pellets followed by 4 g of sodium
hydroxide pellets into a 1 L beaker. A volume of 200 ml of water
complying with the requirements of grade 2 water of (electrical
conductivity less than 0.1 mS/m and resistivity greater than 0.01
MΩm at 25°C) and swirled to mix. This was then quantitatively
transferred into a 1 L volumetric flask, filtered through a membrane
filter using suction filteration apparatus. This was done through
membrane filters of 0.8 µm pore size, made of cellulose ester or
other material that cannot be degraded by sodium tetrahydroborate
solution 9 (HSE, 1994).
Digestion of raw materials
One gram of the raw materials was weighed and digested using 6
ml of concentrated HNO
3,
0.5 ml of concentrated hydrochloric acid
and 1 ml of H
2
O
2
were added to each one in Teflon vessel in order
to dissolve the organic matter. These were placed in the microwave
and digested for 30 min. A multiwave 300 microwave oven (Perkin-
Elmer, Shelton, CT USA) was used for the microwave-assisted
digestion (Davidowski et al., 1990). A predigested spike of arsenic
for arsenic, (or nitrate, nitrite and phosphate) was added to some of
the samples to measure analyte recovery through the digestion
process. The vessels were sealed and placed into the rotor for the
microwave digestion (Davidowski and Sarojam, 1990) (Table 1).
After digestion process, the digestates were transferred to
polypropylene 50 ml auto sampler vials (Perkin Elmer part number
B0193234) and laboratory ASTM type 1 water was added to a final
total weight of 25 g of the container and its content (Davidowski and
Sarojam, 1990). The resulting solution was transferred into a 15 ml
centrifuge tube and made to the mark with deionized water. To
ensure a safe digestion, the multi wave 3000’s IR sensor measures
the temperature of each vessel. If a vessel nears its maximum
operating temperature of 260°C then the microwave oven
automatically decreases the applied power. Also, the pressure
sensor sends data to the multi wave oven controller during the
digestion. The multi wave oven will automatically reduce power if
the maximum pressure of 60 bars was applied (Davidowski and
Sarojam, 1990).
Digestion of brews
No digestion was performed on unfiltered samples prior to
analytical determinations. Portions of 20 ml of the neutralized
filtered brew samples were evaporated to dryness in separate
beakers. The residues were each cooled and extracted with 1 ml
phenol disulphonic acid {prepared from 25 g of phenol crystals
(BDH Chemicals Ltd, Poole, UK), 150 ml of concentrated H
2
SO
4
(Fischer Chemicals, UK), 75ml of fuming H
2
SO
4
(Fischer
Chemicals, UK)} and each mixture heated for 2 h on water bath. All
samples (homemade brews, water, raw materials) and blanks (n=3)
were digested and diluted using the same procedure.
Sample analysis in HGAAS
Instrument calibration in the HGAAS
This was what was done for instrument calibration in the HGAAS, a
10 µg/L As standard was prepared for serial dilutions of a 1000
mg/L stock standard (PE pure, Perkin - Elmer part number
N9300102) (Davidowski and Sarojam, 1990). The solution was
acidified with 20 ml concentrated HNO
3
and diluted to 1.0 L. All
solutions were prepared from analytical reagents: HNO
3
(65%), HCl
(37%), V
2
O
5
(Merck). Commercially available 1000 mg As/L
(prepared from As
2
O
3
in 5 M
HNO
3
;
Tritisol; Merck) was used; All
solutions were prepared with ultrapure water with a specific
resistivity of 18 mohm/cm obtained by filtering double – distilled
water through a milli – Q purifier (Millipore, Bedford, MA, USA)
immediately before use (Davidowski and Sarojam, 1990).
Three samples were prepared using 10 ml aliquots of a water
sample (or a smaller aliquot diluted to 10 ml) from the same
sample. Each of these were spiked with 0.200 mg/L). The arsenic
concentrations were read on a Varian SpectrAA-40 atomic
absorption spectrophotometer in conjunction with Varian VGA-76
hydride generator and absorption cell (Hawthorn, 2011). Once
ignited it was left for approximately 30 min to stabilize. The
instruments were zeroed using the blank and calibrated using the 2
and 4 ng/ml
As standards (Hawthorn, 2011). The 2 ng/ml
standard
was used to check the calibration. It was to be read after every 10
samples. If the result was out by more than 10% calibration was
repeated. The hydride generator was flushed with blank solution for
one minute between standard samples (Hawthorn, 2011).
Sample analysis in HGAAS technique
Aliquote volumes of 10 ml samples were placed in a specially
designed reaction vessel and 6 M HCl in added in the HGAAS.
Before analysis, 4% NaBH
4
solution was added to convert organic
and inorganic arsenic to volatile arsines and care must be taken to
produce the specific metalloid oxidation state before the sample is
introduced into the hydride generation system. This was done by
adding 5.0 ml
of 20% potassium iodide to each standard, 1.25 ml
of
20% potassium iodide to each blank. Standards were made up to
100 ml
with 1 M hydrochloric acid and blanks were made up to 250
296 Afr. J. Pure Appl. Chem.
Table 2. Average concentration (µg/L) of arsenic in various homemade alcoholic beverages and water
[Mean ± SD].
Brew place
Kumi Kumi
[n = 3]
Tap water
[n = 33]
Kangara
[n = 3]
KIBERA
0.27±0.30
0.34±0.01
NA
KARIOBANGI
NA
0.63±0.01
NA
KAWANGWARE
NA
0.58±0.01
NA
GIKOMBA
NA
0.29±0.01
NA
GITHURAI
NA
0.44±0.01
NA
UTHIRU
NA
0.29±0.01
NA
KANGEMI
NA
0.20±0.00
NA
MATHARE
NA
0.29±0.01
NA
KIAMBU
NA
0.51±0.01
NA
KILIMANI
NA
0.44±0.11
NA
RUNDA
NA
0.29±0.01
0.46±0.02
MEAN
0.27 ± 0.30
0.39± 0.138
0.49 ± 0.02
ml
with 1 M hydrochloric acid. After mixing, samples, standards and
blanks were left to stand for one hour before reading. This was to
allow the reduction of As (v) to As (iii) to take place (Hawthorn,
2011).
The arsines were purged from the sample on to a cooled glass
trap packed with 15% OV- 3 chromasorb WAW-DMCSO or
equivalent. The trapped arsines were thermally desorbed, in order
of increasing boiling points, into an inert gas stream that carried
them into the quartz furnace of an atomic absorption
spectrophotometer for detection. The first arsine to be desorbed
was AsH
3
, which represents total inorganic arsenic in the sample, is
purged (via a high purity inert gas) into the optical cell via a gas
transfer line to the atomizer. Quality was ensured through
calibration and testing of the hydride generation, purging and
detection systems (USEPAOW, 1996). This is followed by the AAS
analysis. The AAS alone is limited by interferences, poor
reproducibility, and poor detection limits (Chasteen, 2009).
RESULTS AND DISCUSSION
Concentrations of arsenic (µg/L) various homemade
brews, spirits and tap water
The levels of arsenic levels in various alcoholic brews,
spirits and water from various places determined using
the HGAAS and the results obtained from various
stations are given in Table 2. The average concentrations
were obtained by calculating the mean levels in the ten
samples of each brew analyzed. The results are
presented in Table 2. From the table, the highest levels of
arsenic were obtained in muratina from Kibera which had
the concentration of 0.88 ± 0.03 µg/L. The lowest arsenic
levels were obtained in chang’aa from Kariobangi which
had a concentration of 0.12 ± 0.01 µg/L. Busaa from
Kibera, Kariobangi, Kawangware, Gikomba, Githurai,
Uthiru, Mathare and Kangemi had low levels of arsenic
concentrations ranging from 0.82 ± 0.151 µg/L from
Kariobangi to 0.40 ± 0.01 µg/L from Kibera. Busaa
samples from other areas like Kiambu, Kilimani and
Runda were not available and therefore not analyzed.
This trend was also observed in chang’aa, miti and
muratina. The arsenic levels in Chang’aa ranged from
0.12 ± 0.01 µg/L for chang’aa in Kariobangi to 0.63 ± 0.10
µg/L. mg/L in the brew from Uthiru, while for miti the
arsenic levels ranged from 0.22 ± 0.03 µg/L for miti from
Uthiru to 0.42 ± 0.03 µg/L in the brew from Kariobangi.
The arsenic levels in muratina ranged from 0.40±0.04
µg/L for muratina from mathare to 0.88 ± 0.03 µg/L for the
brew from Kibera. Kumi kumi and kangara had only
values from one station analyzed hence they were not
significant. The average concentrations were obtained by
calculating the mean levels in the ten only one value for
these samples could be obtained since handling these
brews is illegal and only a few samples could be
obtained. These values were found to be below the
maximum allowable limits of 0.01 mg/L for water (EMCR,
2006). The consumers of homemade brews are still at
risk of arsenic poisoning due to its accumulation in the
body with the consistent use of the home made brews.
Standard is based on life – time exposure to arsenic from
drinking water, and takes into account the ability to
measure arsenic and to remove it from drinking water
supplies (Luong et al., 2009).
From Figure 2, busaa had the highest mean
concentration of arsenic of 0.60 ± 0.05 µg/L followed by
muratina with 0.54 ± 0.01 µg/L. kumi kumi had the lowest
concentration of 0.27±0.30 µg/L. All these values were
below the maximum allowable limit set by the
environmental management and coordination (water
quality) regulation (EMCR, 2006) and (KEBS, 2007b) at
0.01 mg/L this was also in agreement with the World
Health Organization Drinking Water Standards
(WHODWS) 0f 0.01 mg/L (Rasul and Jahan, 2010).
Jeremiah et al. 297
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
Concentrations (mg/L)
Brews/Sprits
Figure 2. Overall mean concentrations of arsenic in the
various home made brews/spirits and water.
Table 3. Average concentration (µg/L) of arsenic in various home-made alcoholic beverages and water [Mean ± SD].
Brew place
Busaa [n = 24]
Chang’aa [n = 33]
Miti [n = 24]
Muratina [n = 33]
KIBERA
0.40±0.00
0.27±0.12
0.25±0.02
0.88±0.03
KARIOBANGI
0.82±0.15
0.12±0.01
0.22±0.03
0.57±0.01
KAWANGWARE
0.80±0.22
0.61±0.00
0.71±0.09
0.41±0.00
GIKOMBA
0.71±0.04
0.44±0.02
0.34±0.02
0.61±0.01
GITHURAI
0.71±0.04
0.22±0.01
0.35±0.01
0.41±0.20
UTHIRU
0.58±0.01
0.63±0.10
0.42±0.03
0.63±0.01
KANGEMI
0.34 ±0.01
0.35±0.01
0.40±0.00
0.42±0.00
MATHARE
0.40±0.01
0.43±0.02
0.35 ±0.02
0.40±0.04
KIAMBU
NA
0.37±0.00
NA
NA
KILIMANI
NA
0.35±0.22
NA
NA
RUNDA
NA
NA
NA
NA
MEAN
0.595 ± 0.193
0.379 ± 0.159
0.38 ± 0.1497
0.541± 0.1679
NA = Not analyzed, ND = Not detected.
Kenya Bureau of Standards had 0.1 mg/L for cereal
based alcoholic beverages (KEBS, 2007b) and the same
level applied for unmalted beer (KEBS, 2001a).
In Tables, 3, 4, and 5; statistical test of significance
using analysis of variance (ANOVA) and descriptive
statistics, revealed marked significant differences (p <
0.05) between the arsenic contents of all the home-made
brews and tap water in the eleven samples the Nairobi
County. The analysis was significant, {F (6, 40) = 2.562, p
= 0.034, M = 0.435, SD = 0.1125, MAD = 0.917 and
confidence interval (95 %)}. The median was 0.39 µg/L
and the modes were as follows 0.595, 0.379, 0.38, 0.541,
0.27, 0.39 and 0.49 µg/L. From Tables 3, 4 and 5 since
p < 0.05, F (2.562) > F
critical
(2.3359) therefore, there is a
statistically significant difference in the levels of arsenic in
the homemade brews. A goodness-of-fit test indicates
that the model fits the data very well, and observed and
predicted probabilities of arsenic contamination are
strongly correlated (r
2
= 0.87033). Nairobi County has a
median arsenic concentration of 0.39 mg/L in the
homemade brews, and the arsenic MCL of 0.02 mg/L is
exceeded in 25.75% of the samples. Tap water also
contributed positively towards elevating the levels of
arsenic in the brews/spirits. The home made brews
analyzed in this research had values above the WHO set
limit of 0.02 mg/L for alcoholic beverages (WHO, 1981).
298 Afr. J. Pure Appl. Chem.
Table 4. Frequency table.
Frequency table
Frequency
Frequency (%)
1
14.29
1
14.29
1
14.29
1
14.29
1
14.29
1
14.29
Table 5. ANOVA test on the levels of arsenic in the brews.
Variables
SS
df
MS
F
p
Between
0.397
6
0.066
2.562
0.034
Within
1.033
40
0.026
Total
1.430
46
Table 6. Descriptive statistics for arsenic in homemade brews.
Minimum:
0.27
Maximum:
0.595
Range:
0.325
Count:
7
Sum:
3.045
Mean:
0.435
Median:
0.39
Mode:
0.595, 0.379, 0.38, 0.541, 0.27, 0.39, 0.49
Standard deviation:
0.112006
Variance:
0.01254533
Mid Range:
0.4325
Quartiles:
Quartiles:
Q
1
-->0.379
Q
2
-->0.39
Q
3
--> 0.5155
Interquartile Range (IQR):
0.1365
Sum of Squares:
0.075272
Mean Absolute Deviation:
0.09171429
Root Mean Square (RMS):
0.4471892
Std Error of Mean:
0.04233427
Skewness:
0.06264447
Kurtosis:
1.646748
Coefficient of Variation:
0.2574849
Relative Standard Deviation:
25.74849%
Home-made brews and tap water in Nairobi County are
not safe from arsenic pollution.
Concentrations of arsenic in various raw materials
The mean levels of arsenic in the raw materials used to
make the brews were determined and the results are
represented in the Table 6 and in Figure 3. From the
table muratina plant had the highest concentration of
arsenic at 3.53 ± 0.177 µg/kg followed by jaggery at 2.90
± 0.148 µg/kg. Millet seeds had the lowest concentration
at 1.50 ± 0.19 µg/kg. These were all below the maximum
Jeremiah et al. 299
Figure 3. Mean levels of arsenic in the raw materials.
Table 7. Average concentration (µg/kg) of arsenic in various raw
materials used [Mean ± SD].
Raw materials
Arsenic (µg/kg)[n = 18]
Maize
2.38 ± 0.440
Millet
1.50 ± 0.190
Sorghum
1.33 ± 0.217
Honey
1.53 ± 0.070
Jaggery
2.90 ± 0.148
Muratina fruit
3.53 ± 0.177
limit of 0.4 mg/kg weight set by FAO/WHO (WHO, 1981).
These levels are safe and therefore do not pose health
risks to the consumers. Maize, millet and sorghum used
in the preparation of busaa had high levels of arsenic,
2.38 ± 0.440, 1.50 ± 0.190 and 1.33 ± 0.217 µg/kg
respectively. The mean levels of arsenic in raw materials
used in the home made brews and spirits was collected
and results used to plot the graph in the figure.
The mean levels of arsenic in various raw materials
used were used to determine whether there was any
significant difference between the levels of arsenic in the
various raw materials using the t-test. A one-way analysis
of variance (ANOVA) and descriptive statistics (Tables 7,
8, 9 and 10) were conducted on the raw materials used in
making the homemade brews in Nairobi County. The
analysis was significant, {F (5, 12) = 42.855, p = 0.000, M
= 2.195, SD = 0.893, MAD = 0.742 and confidence
interval (95%)}. The median was 1.955 µg/l and the
modes were 2.38, 1.50, 1.33, 1.53, 2.90 and 3.53 µg/L
From Tables 3, 4 and 5, the P-value of 0.000 is less
than the significance level (0.01) and F (42.855) is
greater than F crit (3.1059), it implies that there were no
significant differences between the levels of arsenic in the
raw materials used. Nairobi County has a median arsenic
concentration of 1.955 mg/L in the raw materials used,
and the arsenic MCL of 0.02 mg/L is exceeded in 40.68%
of the samples. A goodness-of-fit test indicates that the
model fits the data very well, and observed and predicted
probabilities of arsenic contamination are strongly
correlated (r
2
= 0.95676). But there were no significant
differences between the levels of arsenic in raw materials
used.
Conclusion
The levels of arsenic were found to be generally below
the maximum contamination levels of 0.05 mg/L set for
water. The Kenya Bureau of Standards did not have
standards levels for arsenic in the local brews and
alcohols. Hence Kenyan waters and brews are not
heavily contaminated with arsenic. Historical alcoholic
beverages and water quality data bases may be useful in
epidemiological studies that categorize by relative levels
300 Afr. J. Pure Appl. Chem.
Table 8. Descriptive Statistics for arsenic in raw materials used.
Minimum:
1.33
Maximum:
3.53
Range:
2.2
Count:
6
Sum:
13.17
Mean:
2.195
Median:
1.955
Mode:
2.38, 1.50, 1.33, 1.53, 2.90, 3.53
Standard deviation:
0.892967
Variance:
0.79739
Mid range:
2.43
Quartiles:
Quartiles:
Q
1
-->1.5
Q
2
-->1.955
Q
3
--> 2.9
Interquartile range (IQR):
1.4
Sum of squares:
3.98695
Mean absolute deviation:
0.741667
Root mean square (RMS):
2.34148
Std error of mean:
0.364552
Skewness:
0.409809
Kurtosis:
1.38818
Coefficient of Variation:
0.406819
Relative standard deviation:
40.6819%
Table 9. Frequency table.
Frequency table
Value
Frequency
Frequency (%)
1.33
1
16.67
1.50
1
16.67
1.53
1
16.67
2.38
1
16.67
2.90
1
16.67
3.53
1
16.67
Table 10. ANOVA test on the levels of arsenic in the raw materials used.
Variables
SS
df
MS
F
P
Between
11.961
5
2.392
42.855
0.000
Within
0.670
12
0.056
Total
12.631
17
of these nutrients in water in order to assess the
association of this exposure with health outcomes. The
results were higher than the published maximum
permissible contents of arsenic in some home-made
brews and tap water. Therefore consumption of these
homemade brews as food may pose possible health
hazards to humans at the time of the study. Brewers of
home-made brews in these areas should be educated on
the needs to recognize hygiene. The concentrations of
the arsenics in the home-made brews and tap water
obtained in this study would go a long way in providing a
baseline data for the assessment of the levels of arsenic
in the brews and tap water obtained in Nairobi County,
Kenya. Note that the EPA/WHO do not have an arsenic
standard for foods other than bottled water and the
byproducts of animals treated with veterinary drugs (The
University of Arozona, 2013).
ACKNOWLEDGEMENTS
The author wishes to express his sincere gratitude to the
Chief chemist, Government chemist and the chief
engineer, engineer Maina, ministry of public works, and
materials branch for support during the entire research
period when there was inadequate funding. The good co-
operation of the deputy government chemist, Mrs. Okado
and the Head of Departments in both foods and water
and the whole government chemist staff is highly
acknowledged.
Special thanks go to Professor Jane Murungi and Dr.
Charles Onindo of Kenyatta University for their
supervision of the thesis and helpful critical comments
that resulted in the presentation of the data obtained.
Thank you also for your gifted editing, your hard work and
your patience. The author greatly appreciate the typing
assistance of my loving wife Mrs. Rosalia Masime. Lastly,
thanks to the Teachers Service Commission for granting
me study leave with pay, my lecturers, Dr. Ruth Wanjau,
Professor Gerald Muthakia, Dean (SPAS), Dr. Richard
Musau, (Chairman, Chemistry Department), Prof. Hudson
Nyambaka and Dr. Koga (Academic registrar) all of
Kenyatta University, for their support.
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