ACT Science Practice Test 34

More than 5 percent of Americans have asthma, a chronic disease that affects the airways and lungs, causing shortness of breath, wheezing, and sometimes death. In the United States, rates for asthma have steadily increased, nearly doubling during the past 20 years. There is no cure for asthma. Two researchers discuss factors that cause individuals to develop asthma.

Researcher 1

There has long been an association between the allergen Dermatophagoides pteronyssinus (dust mites) and asthma. Evidence for a causal relationship has been supported by bronchial challenge studies and avoidance experiments. Studies have shown that exposure in the child’s own house was the primary determinant of sensitization. Research from around the world has provided evidence about other indoor allergens, specifically cats, dogs, and the German cockroach. These studies showed that perennial exposure to allergens was an important cause of inflammation in the lungs and associated nonspecific bronchial hyperreactivity. Children are being exposed to more perennial allergens now than ever before. Houses are built more tightly and are better insulated and have more furnishings and fitted carpets. In addition, children are spending more time indoors. This increased exposure to allergens, including dust mites, has led to increased sensitization, and more cases of asthma.

Since assays for total serum IgE (immunoglobulin E) became available, it has been clear that patients with asthma have, on average, higher total IgE than patients with hay fever or no allergy. Recent work on patients hospitalized for asthma has suggested that the interaction between rhinovirus and allergy occurs predominantly among patients with total IgE > 200 IU/ml. Thus, the different properties of allergens could influence both the prevalence and severity of asthma.

Researcher 2

It is widely accepted that air pollution exacerbates asthma. For example, when traffic controls were put in place during the 1996 Summer Olympic Games in Atlanta, Georgia, morning peak traffic counts declined by 23 percent. This in turn lowered ozone (O₃) concentrations by 13 percent, carbon monoxide (CO) by 19 percent, and nitrogen dioxide (NO₂) by 7 percent. Associated with these declines in ambient air pollution were drops in Medicaid-related emergency room visits and hospitalizations for asthma (down 42 percent), asthma-related care for health maintenance organizations (down 44 percent), and citywide hospitalizations for asthma (down 19 percent). Despite such striking relationships between exposure to air pollution and asthma aggravation, air pollution has not been regarded as a cause of the disease. Increasingly, however, recent studies have been suggesting that air pollution may, indeed, be a cause of asthma.

The Children’s Health Study (CHS) followed 3,535 children with no lifetime history of asthma for five years. During that period 265 reported a new physician diagnosis of asthma. Analysis of CHS data has shown that children living in communities with high ozone levels developed asthma more often than those in less polluted areas. The hypothesis that ozone might cause asthma is reinforced by a study of 3,091 nonsmoking adults aged 27 to 87 years who were followed for 15 years. The results of this study showed that 3.2 percent of the men and 4.3 percent of the women reported new doctor-diagnosed asthma. The researchers concluded that there was a connection between ozone concentration and development of asthma.

The Great Lakes Science Center (GLSC) has conducted lakewide surveys of the fish community in Lake Michigan each fall since 1973 using standard 12 m bottom trawls along contour at depths of 9 to 110 m at each of seven to nine index transects. The resulting data on relative abundance, size structure, and condition of individual fishes are used to estimate various population parameters that are in turn used by state and tribal agencies in managing Lake Michigan fish stocks.

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Pertussis, commonly known as whooping cough, is a highly infectious disease of the respiratory tract caused by bacteria. The disease spreads by direct contact with secretions from the nose or throat of an infected person, or by breathing in the air when an infected person coughs. Pertussis most easily passes between people in the initial stage of illness, but it can be spread at any time during the course of the illness. Figure 1 depicts the course of pertussis from exposure to recovery.

Figure 1

The number of reported cases of pertussis from 1974 through 2004 is depicted in Figure 2.

Figure 2

The number of reported cases of pertussis in 2004 by age group is shown in Figure 3.

Figure 3

Scientists examined several ingredients commonly used as active agents in sunscreen. The goal of the study was to determine which ingredients are most effective at blocking harmful UV rays.

Scientists used PABA, oxybenzone, octyl salicylate, and a broad-spectrum commercial sunscreen (SPF 45). The samples were exposed to sunlight with wavelengths ranging from 240 to 440 nm. The percent transmittance of UV rays at each wavelength was recorded. The data was collected manually using a spectrophotometer. The results, in 20-nm increments, are shown in Table 1.

Table 1

Figure 1 displays the intensity of sunlight across the spectrum.

Figure 1

In 1975, Thomas B. Fitzpatrick, MD, Ph.D., of Harvard Medical School, developed a classification system for skin type. This system was based on a person's complexion and responses to sun exposure. Table 2 lists the skin types and their characteristics.

Table 2