**Abstract**

Potentially toxic elements (PTEs) contamination in soils threats human wellbeing and ecological health because of their toxicity and bioaccumulation. This research presents a portable Olympus Delta Premium 6000 Series XRF Analyser (Olympus, USA) as a rapid measurement tool (RMT) for PTEs: Cr, Cu, Fe, Pb, Mn, and Zn in contaminated soils in the Niger Delta, Nigeria. A total of 45 crude oil-contaminated soils were collected from three genuinely oil spill sites. The range of measured PTEs concentrations (mg/ kg) in the study sites are as follows: Site 1: chromium (Cr) 54–75, copper (Cu) 5.4–16.6, iron (Fe) 14,841–23,404, lead (Pb) 13.5–21.4, manganese (Mn) 158–555, and zinc (Zn) 32.6–47.2; Site 2: (35–66), (5–16.1), (10166–20,967), (12–17.8), (209–440), (17.6–33.6); and Site 3: (32–115), (6.5–20.8), (7538–22,800), (12–135), (98–338), (19.9–177). The trend of PTEs across the three sites follows the same order: Fe > Mn > Cr > Zn > Pb > Cu. The average concentration values of PTEs in all the 3 sites were higher than background concentration values. Thus, crude oil spill spiked the PTEs concentrations. XRF spectroscopy is recommended as a cost-effective and RMT for PTEs in soils.

**Keywords:** soil, crude oil, pollution, elements, X-ray fluorescence


**2. Demand**

To request a product or service, you must ask for it, afford it, and have a specific plan for purchasing it. Desires are, in fact, the unlimited desires and inclinations that people have for goods and services. Imagine being able to afford something if you could afford it or it was not so expensive. When we make choices, scarcity guarantees that many of our desires will never be met. Demand reflects our plan and vision for the demands that will be met. The amount of goods and services that the consumer plans to buy depends on many factors: commodity prices, related commodity prices, personal income, expected future prices, population, advertising, and preferences.

We must first discuss the relationship between the demand for a good or service and the price. All other factors influencing demand must be kept constant to study this relationship called the Citrus Paribus principle. The demand for a good or service is inversely related to its price; as the price increases, the demand for it decreases, and vice versa. Of course, the rate of demand response to price changes is not the same for all goods, which will be discussed in the topic of elasticity [1].

#### **2.1 Demand curve**

The demand curve is a geometric location of points where the dependent variable is the rate of use of a good, and the independent variable is the price of that good; in general, the demand curve shows the maximum demand for a good at different prices and also represent the ultimate price for a certain amount of a good. Usually, the price variable is shown on the y axis and the amount of goods or services on the x-axis (**Figure 1**).

This shows the maximum amount someone is willing to pay for a small increment in consumption rate. Care should be taken in using the "demand" to mean the amount of consumption of a particular good or service at a specific price and to use it to mean a range of corresponding values in the price range (for example, one point on the demand curve versus the whole Points on the curve). The demand for a good or service is a function of its relative price and buyers' income. The demand curve is a twodimensional representation of this process. Responding to price changes is moving along the demand curve and responding to changes in revenue as the entire demand curve changes and shifts (**Figure 2**). Some of the characteristics of the demand side that should always be kept in mind when using the demand curve in healthcare, especially when making normative statements about well-being, are: Uncertainty

**Figure 1.** *Demand curve.*

*Demand for Health and Healthcare DOI: http://dx.doi.org/10.5772/intechopen.98915*

**Figure 2.** *Change in demand curve.*

on the part of the consumer about the likelihood of future illness; Side effects, the effectiveness of treatment methods and their possible cost. When sick, people experience anxiety, disability, suffering, and pain that may not be considered in the theory of desirability; It is also important to note that there may be an external demand for care and treatment of a person in addition to their need; And the fact that the price at which the applicant responds to the service or goods may in no way be an accurate reflection of the final cost of providing that product or service to the service provider.

We can also consider the demand curve as a payment ability curve that measures the ultimate benefit. This curve shows the highest price a person is willing and able to pay for the last unit purchased. If there are fewer goods available, the highest price that a person is willing and able to pay for a larger unit will be high. But as the quantity of available goods increases, the ultimate benefit of each additional unit decreases, and the highest price offered on the demand curve decreases.

In addition to the price of the product in question, which is inversely related to the demand for that product, we can examine the relationship between the demand for a product and other factors in the space of the demand curve.

**Prices of other goods:** The amount of goods or services that consumers plan to buy depends in part on the prices of other goods and services. In this case, there are two types of goods: substitute goods and complementary goods. Two substitute goods can be used instead of each other, and if the price of one of them increases, the demand for that product will decrease, and people will be more likely to demand a substitute product. For example, if beef and chicken are two substitutes, as the price of beef increases, so makes the demand for chicken.

A complementary good is a good that is used with another commodity, and if the price of one of these commodities increases, in addition to the demand for that commodity, the demand for the other commodity also decreases.

**Income**: Assuming other factors are constant when people's incomes increase, they buy more goods and services, and vice versa. Demand increases as income increases are normal goods, and goods for which demand decreases as income increases are called inferior goods. But in general, it can be said that the demand for health goods and services has little to do with income. Because medical goods and services provide their health reserves, and as a result, people's income cannot have a significant impact on demand for these goods. However, rising incomes will increase the demand for luxury medical services.

**Population**: Demand also depends on the size and age structure of the population. If the population increases, the demand for all goods and services increases,

and the population decrease. The demand for goods and services decreases. At the same time, as other factors remain constant, as the population in a particular age group increases, so makes the demand for goods and services used by that age group.

**Consumer's Preferences**: Demand also depends on consumer preferences. Preferences are people's tastes and attitudes towards different goods and services. Preferences are formed based on previous experiences, genetic factors, propaganda, religious beliefs, and other cultural and social factors [2, 3].

### **2.2 Medical goods**

Medical care consists of countless goods and services that maintain, improve, or restore a person's health. For example, a young man may have wrist surgery to repair a torn tendon so he can return to work, an older woman may have cataract surgery to improve her vision, or a parent may have to Bring their child to a healthcare center for an annual dental checkup to prevent future problems. Prescription drugs, prescription glasses, and dentures are examples of medical supplies, while surgeries, periodic physical examinations, and visits to medical professionals are examples of medical services. Preventive and medical care are heterogeneous, making it difficult to measure and quantify medical care units accurately. Medical care services have four characteristics that distinguish these from other goods and services: intangibility, inseparability, inventory, and inconsistency.

Intangibility means that the five senses are incapable of evaluating medical services. Unlike new shoes, a vegetable salad dinner, or a new cell phone, the consumer cannot see, taste, or touch medical services. Indivisibility also means that the production and consumption of a medical service take place simultaneously. For example, when you see an ophthalmologist for an examination, you use ophthalmic services right at the time of production. In addition, a patient is often seen as both a producer and a consumer. Inventory is directly related to inseparability. Because the production and consumption of a medical service occur simultaneously, healthcare providers cannot store or maintain medical services. For example, a physiotherapist cannot provide a list of different physiotherapy services to meet demand during busy times. Finally, inconsistency means that the variety, composition, and quality of medical services are very different. Although different people may see a doctor simultaneously, there are various reasons for visiting a doctor. One person may see a doctor because of a typical physical problem, while another may see a doctor because of a heart attack. The combination of prescribed medical care or the frequency of its use can vary significantly from person to person and at different times [4, 5].

**Demand for healthcare:** Demand requires people to seek a service they can afford and are willing to pay for it. The need for healthcare is the care that doctors believe is essential for a person to stay healthy or healthy. Sometimes, patients think they need healthcare, but doctors believe they cannot benefit from such care. Sometimes the doctor believes that there is a medical need, but the patient does not consult his doctor because he prefers not to receive treatment or that he has not recognized the need. Even if patients have as much knowledge as doctors, their demands may be different from their needs.

The following factors affect the demand for healthcare:

*Demand for Health and Healthcare DOI: http://dx.doi.org/10.5772/intechopen.98915*

III.Price or cost of use

IV.Income

V.transportation cost

VI.waiting time

VII.Quality of care (based on patient perception)

The use of healthcare depends on demand and availability. If planners allocate resources based on need rather than demand, they may find themselves in a situation where some services are underused, and some services are overused.

Just as the healthcare market is different from other commodities, so is the demand for healthcare different from the simple demand model. One of the differences is that healthcare is not demanded because it is self-satisfying. After all, healthcare itself does not lead to satisfaction. Instead, healthcare is in demand because people are satisfied with their activities when they are healthy. So the demand for healthcare is a derived demand.

Patients' perceptions of their need and capacity to benefit from healthcare are strongly influenced by physicians and healthcare providers. Although in economics, it is assumed that consumers can make informed decisions about their consumption patterns, healthcare consumers delegate this decision-making power to healthcare workers who are more aware of them. This phenomenon is due to information asymmetry between healthcare providers and patients, which carries the risk of induced demand by providers to increase revenue. Another complication stems from the fact that healthcare is highly heterogeneous. Each patient has a relatively different combination of pain and symptoms. Therefore each patient needs to purchase a fairly different package of care that both the patient and the physician have uncertainty about its effectiveness in meeting the need.

Another critical difference is that many health services are paid for by third parties. Payments by third parties or insurance companies Although they significantly increase people's purchasing power for healthcare, it is also important to note that they can lead to ethical risks and increase demand for services that patients may not need.

Demand for healthcare depends on the level of consumption of an individual in case of illness; the amount of consumption can differ according to the factors affecting the demand, such as income, service price, education, norms, social traditions, and quality. A person's decision to use or use services is related to his or her illness/injury status rather than healthcare. Developing countries are focused on promoting healthcare as an essential policy to improve health outcomes and fulfill international obligations and universal coverage of health services. However, many policies have focused more on improving physical access than on the demand-side healthcare needs pattern. In low-income countries, allocating scarce financial resources is based on clear criteria for the impact of investment in the health sector on service demand.

In these countries, due to the lack or weakness of social security systems, the occurrence of the disease leads to increased health costs and reduced labor productivity and leads to a loss of household welfare. In developed countries, due to insurance, many health services are used with minimal consumer participation in the payment; however, in developing countries, concerns about less use of health services, to the extent of supply. Or poor access is associated. However, even in health services, due to various barriers on the demand side, related to the cost

of treatment, travel costs, and quality of services, the rate of exploitation is low. Also, the importance of a person's health status in a clinical context is related to the analysis and social evaluation of a person's health and social environment. Studies have shown that the risk of death is related to people's perception of the health importance of maintaining it. Since one of the priorities of health policymakers is to improve people's health, various factors that directly and indirectly affect the demand for health services should be examined more carefully. Identifying the factors influencing individuals' decision to request healthcare services and choosing from different providers. Therefore, evaluating the determinants of demand for health services will introduce and implement appropriate incentive schemes to encourage better health services. Because health is one of the essential components of human capital and healthy human beings are the center of sustainable development, health can significantly increase the ability of individuals to perform various activities, including productive activities. As a result, people are looking for health. At the individual level, health is mainly influenced by multiple factors such as biological factors, lifestyle, purchased non-medical services, purchased medical services and goods, and different socio-economic characteristics. People's understanding and expectation of healthcare quality are essential because the perceived quality of health services often affects health services' behavior and consumption patterns [6].


**4.2 Oxidative stress in adjuvant arthritis**

In the development of AIA, not only immunological and inflammatory pathological changes are involved, but also the redox homeostasis is shifted toward increased production of ROS and RNS. Overproduction of ROS and RNS damages lipids, proteins, and DNA (also exhausts the natural enzymatic and nonenzymatic antioxidant defense), which is possible to detect with different markers of oxidation in biological structures. In human RA OS-mediated damage to lipids, proteins, and DNA and changes in enzymatic and nonenzymatic antioxidant defense are extensively studied. AIA in animals resembles the OS caused damage in human rheumatic diseases; therefore, it is a very useful tool to study process of OS during autoimmune diseases. Since there has been no standard therapy to reduce OS damage in diseases established yet, AIA could be a promising candidate for developing this type of therapy.

elevated levels of F2-isoprostanes observed in such diseases. Quantification of F2 isoprostanes as pathophysiological markers is suitable for the investigation of lipid peroxidation in human diseases and provides an interesting biomarker of antioxidant efficacy in diseases where OS might be involved [59]. There are only few evidences about F2-isoprostanes in animal models of RA. In one of our previous experiments, we have measured an elevated level of F2-isoprostanes in plasma of AIA rats, which were significantly increased compared to control healthy animals [60]. In a CIA model, authors investigated the ability of grape seed proanthocyanidin extract (GSPE) to reduce the development of mice arthritis. They have found that CIA significantly increased the level of 8-isoprostane in plasma. Plasma levels of 8-isoprostane and serum level of collagen type II-specific IgG2a in GSPEtreated mice were significantly decreased than those in the control mice [61]. Authors demonstrated that F2-isoprostanes are increased also in the urine of CIA mice [62]. F2-isoprostanes as an important marker of lipid peroxidation should be more extensively studied in AIA animal models, to obtain a better picture about the

*Markers of oxidative stress (malondialdehyde (MDA) and 4-hydroxynonenal (HNE) in the brain of arthritic*

**Oxidative stress in brain MDA (μg/g tissue) HNE (ng/g tissue)** CO 5.38 0.73 3.26 0.17 AIA 10.12 1.01\*\*\* 4.78 0.5\*\* *Values are expressed as average standard error of mean, statistical significance (ANOVA-Tukey-Kramer post*

*Impact of Oxidative Stress on Inflammation in Rheumatoid and Adjuvant Arthritis: Damage…*

Protein carbonyls (aldehydes and ketones) are produced directly by oxidation or via reactions with other molecules generated by the oxidation process. Autoimmune attack, resulting from abrogation of self-tolerance, is involved in many human diseases. Autoimmune disease may be either organ specific (type 1 diabetes, thyroiditis, myasthenia gravis, and primary biliary cirrhosis) or systemic (RA, progressive systemic sclerosis, and systemic lupus erythematosus). Nearly all these diseases have autoantibodies. Autoantibodies are typically present several years prior to diagnosis of SLE and serve as markers for future disease. Inflammation, infection, drugs, ROS, and environmental factors induce formation of neo-antigens [63]. The protein thiol groups were 59% diminished by AIA. The protein carbonyls content, an indicative of protein damage, was increased by arthritis (41%). Protein damage in both liver and brain was estimated as the tissue content of protein carbonyl groups. Corroborating previous results, arthritis increased protein damage in both tissues, 55% in the liver and 51% in the brain [64]. Authors Hemshekhar et al. [65] also showed a significant decrease in total protein thiol content with reference to saline-fed rats up to 51 and 36.05%, respectively, in liver and spleen homogenates of arthritic rats [65]. In a study about protective effects of green tea extract in AIA rats, authors detected a significant OS-caused damage to proteins and lipids in the liver, brain, and plasma [66]. The antioxidant defense, reduced in arthritis, is improved by the green tea treatment, as shown in the restoration of the GSH and protein thiol levels and by the tendency for normalizing the activities of the antioxidant enzymes. In arthritis rats, we found a significant increase of protein carbonyls in plasma [66–69] (**Table 1**). This finding emphasizes the role of OS in

similarity with human RA.

*hoc test): \*\*p < 0.01, \*\*\*p < 0.01 vs. CO.*

*DOI: http://dx.doi.org/10.5772/intechopen.89480*

*animals measured on day 28).*

**Table 2.**

*4.2.2 Oxidation of proteins*

**203**


**3. Using MALESAbrain in problem-based discussion**

To illuminate the learning algorithm in MALESAbrain, we use an example to explain the problem-based discussion guided by the learning system. In this section, we explain how an educator set up the learning thresholds, and then discuss the functions in the learning system.