Air pollution in a chemical fertilizer complex in Nigeria: The impact on the health of the workers

Volume:4
Issue:2
Year: 2005
Dr Godson R.E.E. Ana1, PhD, MPH, M.Eng, BSc, MRSPH, MIFEH, MAPHA.
Professor Mynepalli K.C. Sridhar1 PhD, MSc, BSc, FRSH, MCIWEM, C.Chem.
Dr Joshua F. Olawuyi1 PhD, MSc, BSc, MIS, MIEH, FSS.
1Department of Epidemiology, Medical Statistics and Environmental Health, Faculty of Public Health,
College of Medicine, University of Ibadan.
Correspondence: Dr Godson R.E.E. Ana, Department of Epidemiology, Medical Statistics and Environmental Health, Faculty of Public Health, College of Medicine, University of Ibadan, Ibadan, Nigeria. Telephone: 234-8037146436.

Abstract

A study was carried out on the nature and levels of air pollution in a chemical fertilizer complex at One, near Port Harcourt in the eastern part of Nigeria. The fertilizer complex, with a work force of about 3,000, produces per day, a total of around 3,500 tonnes of ammonia, urea and NPK (Nitrogen, Phosphorus, Potassium) formulations to meet the fertilizer needs of the country.
Air samples were collected at periodic intervals from selected sections in the industrial complex. Ammonia and particulate  emissions constituted the major air pollutants. Among the various sections in the industrial complex, the urea plant produced the highest ammonia emissions with a mean value of 459.1664.5 mg/m3, while the bulk blending plant where NPK formulations are made produced the highest total suspended particulates (TSP) with a mean value, 26,085.7611,966.9 mg/m3. Other sections in the complex emitted relatively low levels of ammonia and TSP.
A health survey by questionnaire involving 384 randomly selected plant workers and an equivalent number of controls living away from the industry revealed that the industrial complex workers complained more (p<0.05) of respiratory problems (66.1%) and eye problems (22.6%) besides skin irritation and other common complaints. The populations living further away from the complex reported relatively low levels of these ailments as compared to the exposed populations (p<0.05). These figures agreed with hospital records where the populations attend for their treatment.
Keywords: Air pollution, environmental health, communities, fertilizer industry, health risks, Nigeria, workplace.

Introduction

Globally, fertilizer consumption has, over the past few decades increasingly shifted towards developing regions. The main forces responsible for this shift are the introduction of environmental legislation restricting the use of fertilizers in many developed countries and a significant growth in fertilizer demand in developing regions as a result of an unprecedented growth in population in most of these regions, particularly in Asia (UNU/INTECH, 1999).
In China for instance, nitrogen fertilizer produced in small-scale plants dominate the structure of the chemical industry (UNU/INTECH, 1999). The main pollutants of the chemical fertilizer industry in China are described mainly as wastewater and air emissions in addition to limited solid waste (Agro-chemicals report, 2002). Another Asian example is Turkey, which has a well developed fertilizer industry. It has six major fertilizer producers on the local market, including two private manufacturers. Nitrogen consumption constitutes 64% of the total NPK (Nitrogen, Phosphorus, Potassium) fertilizer consumption (Ejupoola, 1992).
In Africa, Morocco is the leading producer and the world’s largest exporter of phosphate rock and phosphoric acid. Over the last two decades, trade in processed phosphates has increasingly replaced the phosphate rock trade. The main destination for phosphoric acid exports is Western Europe. The main exporters of phosphoric acid are the United States, Tunisia and Morocco (Louis,1997). According to recent estimates, the phosphate industry sells approximately 200,000 tons of silicofluorides (hydrofluorosilic acid and sodium silicofluoride) to US communities each year for use as a water fluoridation agent (Coplan and Masters, 2001). The health effects associated with the phosphate fertilizer industry include poisoning of domestic animals caused by fluorine in smoke; industrial fluorosis in livestock is a disorder known by veterinarians in all industrialized countries (Connet, 2003).
The chemical fertiliser industry in Nigeria is at an infant stage. Of the two existing companies, the National Fertilizer Company of Nigeria (NAFCON) described here is a major one and is located at Onne (4.490 and 4.50 N and 6.590 and 7.00 East of Greenwich Meridian), 30 Km away from Port Harcourt in the eastern part of Nigeria. It utilises a variety of raw materials such as natural or synthetic gas (methane), atmospheric nitrogen, steam and sand as filler material in the production of various formulations. The major products (per day) are ammonia (1,000 tonnes), urea (1,500 tonnes), and NPK formulations (1,000 tonnes).
The main sections where gaseous and particulate emissions are reported are the ammonia plant, urea plant, NPK plant, bulk blending plant, bulk storage plant, and the bagging area. Potential sources for leaks in the ammonia plant are the refrigeration loop, storage areas, flanges, valve packing, and the pump and compressor seals. The gaseous emissions from the ammonia plant include reformer and boiler flue gases, excess carbon dioxide, condenser stripper vapour and ammonia discharge. The gases coming from the reformer are vented into the atmosphere with a mixture of CO2 (20%) and O2 (3-4%). Most of the CO2 is recovered and recycled in the process.
The condensate of the process water contained some CO2, methanol and other dissolved gases, which are usually stripped. In the urea plant there are two possible sources of emissions, viz. the high-pressure scrubber and the granular stack. Some amounts of methane, hydrogen, ammonia and CO2 are released. The wet scrubbers also release some particulate urea through the vent. In the NPK plant the tail gas scrubber is the only source of emission of ammonia, particulates and small quantity of fluoride. In various operations, e.g. granulation, drying, mixing and cooling, some amounts of dust and fumes are generated.
While the company has installed the recommended air pollution control devices for dust collection and fume scrubbing, the air is still laden with pollutants and people complain of a pungent smell and irritation of eyes and skin. A large volume of literature is available on the health effects of ammonia and particulate matter from industrial emissions. Hall et al (1995) reported that in a total of 263 events studied involving ammonia, 600 people were injured while 4 died. The major health effects were respiratory, eye irritation and skin irritation (Wieslander et al, 1994; Hall et al, 1995). Tabakova et al (1993) from Bulgaria, referring to air pollution due to ammonia at Vrata, reported that ammonia and hydrogen sulphide have direct effects on acute respiratory morbidity among children. Total Suspended Particulates (TSP) and health effects are well documented and most of the reports centred on respiratory problems (Abbey et al, 1993), and mortality (Schwartz and Dockery, 1995).
There has been no documentation of the fertilizer industry emissions and the associated health effects from Nigeria. The objective of this study was to assess the nature and levels of air pollutants characteristic of the fertilizer complex at Onne, and to elicit information from the plant workers concerning their health problems.

Materials and Methods

Study LocationThe study was carried out in and around the industrial complex of the National Fertilizer Company of Nigeria (NAFCON) and extended to a 5km radius around the complex. The major sections of the complex used in the study were: the ammonia plant, the urea synthesis plant, the bulk blending plant, the bulk storage plant and the two control areas viz. control(1), located about 1 km away from the processing area and control (2), located in the corporate building 2km away from the factory premises.
At the ammonia plant, ammonia is produced through the Haber process, which involves a reaction between hydrogen and nitrogen in the presence of steam and temperature over 8008C. This process involves the following stages: desulfurisation, reforming, carbon dioxide purification, synthesis, and refrigeration. At the urea plant, the major raw materials used as feed are ammonia and carbon dioxide and urea is produced through the combination of exothermic and endothermic processes that are divided into the urea synthesis and granulation. Usually there is more ammonia from this plant arising from leakages and periodic venting.
At the NPK plant, ammonia, phosphoric acid, urea, potash, and sand (filler material) are the basic raw materials used in the production of the different formulations of NPK fertilizers. This plant and the bulk blending plant (where other complex fertilizers are produced) and the bulk storage plant are characterized by dusty premises.
Materials
Air samples were collected cross sectionally from 7 points located at the ammonia plant, urea synthesis plant, NPK formulation plant, bulk blending plant, the bagging area and control areas (1) and (2).
For ammonia determination, all points were sampled except for the bulk blending and bulk storage plants. A wet test meter (model 63115, Precision Scientific Inc, USA) was used to draw air into a double-orifice-fitted glass bottle containing a specially prepared medium of weakly bonded boric acid, known to loosely trap free ammonia molecules. This medium was then transferred to the laboratory for ammonia determination.
For TSP determination, all the points were sampled except for the ammonia plant. A high volume sampler (model GL 2000 HX, Fisher scientific company) was used to draw air through a glass fibre filter of pore size 0.45m by means of a blower/pump with a flow rate between 1.13 and 1.70 m3/min. This arrangement enabled collection of particles with a size range of 100 – 0.1m diameters. Prior to the collection of samples, the equipment was standardized after adjusting for atmospheric temperature and pressure using recommended standard procedures (Fertilizer
Association of India, 1987).
Table 1.0 Ambient Ammonia Levels in the Atmosphere

Sampling points	Sample 1	Sample 2	Sample 3	Mean +/-SD
Control Area 1	12.6	18.90	10.80	14.1064.25
Control Area 2	6.24	10.63	4.98	7.2862.97
Ammonia Plant	24.00	16.60	60.20	33.60623.33
Urea Synthesis plant	528.9	401.8	446.7	459.13664.46
NPK Plant	171.05	169.46	142.33	160.95616.14

 

 

Methods

The ammonia, which was trapped into the boric acid medium, was determined by volumetric analysis through back titration against hydrochloric acid using phenolphthalein and bromo cresol green as indicators and appropriate standards. The TSP was determined gravimetrically after proper conditioning of the filter, which involved exposure to a light source, inspection for pinholes, particles, and other imperfections, followed by equilibration of the filter papers for 24 hours under regulated oven temperatures (filter environment). The data were computed for mean 4 hour weighted average and statistically analysed. Owing to similarities in technology adopted, the methods followed were those recommended by the Fertilizer Association of India (1987).
The assessment of perceived health effects on the plant workers was undertaken by a health survey using a questionnaire. A sample size of 384 plant workers selected randomly with 50% proportion at 95% confidence interval was used for the survey. The questionnaire addressed demographic features, occupational history, level of education, awareness of pollution effects and other relevant iinformation. The perceived health effects such as eye irritations, skin and respiratory disorders were compared with those from the hospital records in the area where the workers get their treatment. Similarly, information was also obtained from control populations near the industry. In addition, to validate the results, hospital records were collected from clinics, both within and outside the industrial complex, for the exposed population (plant workers) as well as outside clinics in Port Harcourt city for the non-exposed population (non-plant workers).

Results

Ammonia and Total Suspended Particulates (TSP) levels in the air The ammonia levels in the air at various sections of the  industry are given in Table 1.0. The results indicate that the urea plant emits the highest level of ammonia followed by the NPK formulation plant. Using the Mann-Whitney u test, no significant differences were found between the ammonia concentrations at the ammonia, urea, and NPK plants and the control areas (p>0.05). As would be expected the ammonia levels were higher in the control area (1) within the complex, than at the control area (2) located about 2km away from the industrial operations.
TSP levels (Table 2.0) were found to be highest in the bulk blending plant followed by bulk storage plant, the NPK formulation plant and the urea granulation plant. There was no significant variation between the controls and the various plant units (p>0.05) (Mann-Whitney u test).
Health Impacts of the Emissions Analysis of the questionnaire responses from 384 plant workers indicated that the majority of the workforce in the operations were male (91.0%), 32.4% were in the age group of 26-30 years, 70.5% spend 8 hours per day at work. 222 workers (57.9%) reported general health problems since they began work and 146 (37.9%) reported to be suffering for more than a year.
Among the more striking complaints by the workers since they commenced work were: respiratory disorders as reported by 254 (66.1%), skin disorders reported by 94 workers (24.4%), and eye disorders reported by 87 workers (22.6%). The other common health problems reported were: malaria, cold and headache (29.3%), chest pain and respiratory disorders (15.9%), chest pains, and eye and skin disorders (10.2%) (Figure 1.0). The Mann-Whitney u test indicated that there were significant differences between the exposed (cases from clinical records) and the control groups (p<0.05) as well as between the perceived exposed (cases from
interviews) and the control groups (p<0.05) for all the reported morbidity cases. There were strong associations (p <0.05) between eye and respiratory disorders and the industrial operations the workers performed.
Table 2.0: Total Suspended Particulates (TSP) in the Atmosphere

Sampling points	Sample 1	Sample 2	Sample 3	Mean +/-SD
Control Area 1	115.65	101.87	125.01	114.18+/-11.64
Control Area 2	110.35	124.15	104.23	112.91+/-10.20
Urea Granulation Plant	665.46	533.11	498.34	565.64+/-88.18
NPK Plant	2954.44	954.44	11684.23	1864.37+/-1012.1
Bulk Blending Plant	14987.0	38764.0	24506.0	260875.7+/-11966.9
Bulk Storage Plant	2342.05	5133.06	3684.25	3720.09+/-1396.3

Discussion

The study reported here is the first of its kind in Nigeria.
Most of the ammonia affecting the workers in this area arises from the urea plant due to leakages and the periodic venting of the plant. These levels, though lower than the Federal Environmental Protection Agency’s (FEPA’S) recommended limits of 3000 mg/m3 (from stationary sources), could still produce deleterious health effects on the staff working within this plant owing to persistent nature of their exposure.
The high values of Total Suspended Particulates (TSP) recorded at the bulk blending plant was consistent with visual observations made at the premises of the plant, which indicated very dusty conditions. The values recorded were higher than the National Air Pollution Standards set by the FEPA in 1991, which sets a limit of 0.15-0.5 mg/m3 (Table 3.0).
Table 3.0. Air Quality Standards in Nigeria

Pollutants	Ambient Limits	Limit from stationary sources (For 24 hrs)
Particulates	250 mg/m3 (Daily average of daily values 1 hour)	0.15-0.5 mg/ m3
Sulphate Oxides (SO2)	0.01 ppm (26mg/m3) 0.1 ppm (260 mg/m3) (Daily average of hourly values 1 hour)	0.05 – 0.5 mg/ m3
Non-methane hydrocarbon	160mg/m3 (Daily average of 3-hourly values)	2.0 – 5.0 mg/ m3
Carbon monoxide	10 ppm (11.4 mg/m3) 20 ppm (22.8mg/m3) (Daily average of hourly values 8-hours)	1.0 – 5.0 mg/ m3
Nitrogen Oxides (NO2)	0.04 ppm - 0.06 ppm (75.0–113 mg/m3) Daily average of 1-hourly values (range)	0.004 – 0.1 mg/ m3
Photochemical Oxidant	0.06 ppm (Hourly values)	5133.0

Figure 1.0: Health Disorders Observed and Perceived among the Workers.

The control groups, especially control (2) which is about 2 Km away from the industrial complex, are at low risk.

The health implications, particularly at the urea and bulk blending plants, are very significant and precarious as the workers in these plants were not in the habit of using protective devices even though these were provided. This study also revealed that while workers reported always using the protective devices, in reality they seldom wear them at work.

The findings from this study are of both epidemiological and toxicological importance. There was an indication that the health effects such as skin disorders and respiratory tract infections were associated with exposure to high concentrations of the atmospheric pollutants, viz. ammonia and total suspended particles. This was found to be in agreement with the findings of Abbey et al (1993), Wieslander et al (1994) and Hall et al (1995) which focused on the health effects associated with exposure to atmospheric emissions and particulates. It was also discovered that there were strong associations between eye and respiratory disorders and the nature of work performed by the plant workers, especially for those who were not in the habit of wearing the protective devices. This is in addition to the fact that the degree of the health problem could be more severe at plant locations with higher concentrations of ammonia and suspended particulate matter.

Based on this, certain mitigation measures were suggested which include health education to plant workers, routine inspection of plant staff safety habits, regular auditing of the air pollution control devices and periodic monitoring of the air quality to ensure continued compliance with recommended limits.

Conclusions

• Most of the ammonia affecting the workers in the fertilizer industrial complex was from the urea plant arising from leakages and the periodic venting of the plant.
• The observed levels of ammonia, though lower than FEPA’S recommended limits of 3,000 mg/m3 (from stationary sources), could still produce deleterious health effects on the staff working within this plant because of the persistent nature of their exposure.
• The bulk blending plant, which recorded the highest TSP levels (26,085.7611,966.9 mg/m3), was mainly responsible for the dusty conditions commonly observed in the industrial environment.
• Health effects, such as skin disorders and respiratory tract infections, were associated with exposure to high concentrations of the atmospheric pollutants, viz. ammonia and total suspended particles.
• Significant associations were observed between eye disorders, respiratory disorders and the nature of the work performed by the workers especially for those who were not in the habit of wearing the protective devices provided.
• Significant differences were observed between the degrees of morbidity cases among the exposed workers compared to the non-exposed controls. To safeguard the health of the plant workers, there must be regular occupational health monitoring, health education of workers, routine equipment auditing/maintenance and/or periodic production process review.

Acknowledgements

We express our sincere gratitude to the management of NAFCON for supporting this research by granting us access to their industrial complex and permitting us to use their field equipment and laboratory facilities.

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