Why are nitrogen oxides considered harmful to humans?

Nitrogen dioxide is an irritant gas, which at high concentration cause inflammation of the airways. ... Nox gases react to form smog and acid rain as well as being central to the formation of fine particles and ground level ozone, both of which are associated with adverse health effects.

Nitrogen dioxide levels above a certain limit can harm the human respiratory system, increasing a person's sensitivity to and severity of respiratory infections and asthma. Chronic lung disease can be caused by long-term exposure to high levels of nitrogen dioxide.

Explanation:

the  frequency of a wave represents  the number of wavelengths that pass a specific point per second. the unit for  frequency  is hertz (hz).

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americans began to notice growing differences between the northern and southern sections of the country. there were more people living in cities in the north, which made it more urban. more people lived on farms in the south, which made it more rural. while many people were farmers in the northern states, there were now other ways to make a living, such as working in mechanical cotton gins factories manufacturing cloth, tools and other goods. people in the north supported high tariffs on goods imported from europe because the extra cost encouraged people to “buy american” instead. in the southern states, planters did not like tariffs because they sold most of their production to europe and bought their tools from there as well. southerners believed the protective tariff was something that only northern factory owners keep their profits high. so the southern politicians came up with an idea. they would opt out. they would simply ignore the protective tariff. it was ‘null and void’ in south carolina. the state would not collect the taxes on goods imported into south carolina, no matter what the president said they had to do. this decision led to the nullification crisis.