In only 200 years, the world's urban population has grown from 2 percent to nearly 50 percent of all people. The most striking examples of the urbanization of the world are the megacities of 10 million or more people. In 1975 only four megacities existed; in 2000 there were 18. And by 2015 there were 22.

The growth in urban areas comes from both the increase in migration to the cities and the fertility of urban populations. Much of urban migration is driven by rural populations' desire for the advantages that urban areas offer. Urban advantages include greater opportunities to receive education, health care, and services such as entertainment. The urban poor have less opportunity for education than the urban nonpoor, but still they have more chance than rural populations.

Urban fertility rates, though lower than rural fertility rates in every region of the world, contribute to the growth of urban areas. Within urban areas, women who migrated from rural areas have more children than those born in urban areas. Of course, the rural migrants to urban areas are not a random selection of the rural population; they are more likely to have wanted fewer children even if they had stayed in the countryside. So the difference between the fertility of urban migrants and rural women probably exaggerates the impact of urban migration on fertility.

The urban environment is an important factor in determining the quality of life in urban areas and the impact of the urban area on the broader environment. Some urban environmental problems include inadequate water and sanitation, lack of rubbish disposal, and industrial pollution. Unfortunately, reducing the problems and ameliorating their effects on the urban population are expensive.

The health implications of these environmental problems include respiratory infections and other infectious and parasitic diseases. Capital costs for building improved environmental infrastructure – for example, investments in a cleaner public transportation system such as a subway – and for building more hospitals and clinics are higher in cities, where wages exceed those paid in rural areas. And urban land prices are much higher because of the competition for space. But not all urban areas have the same kinds of environmental conditions or health problems. Some research suggests that indicators of health problems, such as rates of infant mortality, are higher in cities that are growing rapidly than in those where growth is slower.

29: Proceeding urbanization in the EU member states, 2015 (http://ec.europa.eu/eurostat/documents/2995521/7020151/3-05102015-BP-EN.pdf/bf18a8b3-998c-476d-b3af-58292b89939b)

Lado et al. (2008) present the results of modelling the distribution of eight critical heavy metals (arsenic, cadmium, chromium, copper, mercury, nickel, lead and zinc) in topsoils using 1588 georeferenced samples from the Forum of European Geological Surveys Geochemical database (26 European countries). High values of Cr and/or Ni are mainly found in central Greece, northern Italy, the central Pyrenees, northern Scandinavia, Slovakia and Croatia and show a strong correlation between the contents of Ni and Cr and the magnitude of earthquakes. The seismic activity is indirectly correlated with heavy metal concentrations – such materials provide high quantities of Ni and Cr to the soils by weathering processes. Cadmium, Cu, Hg, Pb, Zn present a high concentration in Central Europe and are mainly related with agriculture and with quaternary limestone. The use of fertilizers, manure and agrochemicals are important sources of these elements. They are also inversely correlated with distance to roads (Lado et al., 2008).

Although there are 700 emerging pollutants described in the European environment (NORMAN, 2014), until now, they are only taken under consideration in the aquatic environment. Their presence and concentration in the terrestrial ecosystem is unknown as is the potential risk for the environment. Aerial transport of pollutants from industrial and urban sources is even more difficult to monitor because their distribution and the fall out is not easily known.

More than 3000 different types of pesticides have been used in the European agricultural environment in the past 50 years. It has been estimated that less than 0.1% of the pesticide applied to crops actually reaches the target pest; the rest enters the environment, contaminating soil, water and air, where it can poison. Heavy metal content in European soils (Lado et al. 2008). 95 otherwise adversely affect non-target organisms (Pimentel and Levitan, 1986). Furthermore, many pesticides can persist for long periods in an ecosystem – organochlorine insecticides, paraquat, deiquat for instance, were still detectable in surface waters 20 years after their use had been banned (Larson et al., 1997). Few studies have been carried out monitoring the mixtures of pesticides present in our soils. Oldal et al. (2006) and Ferencz and Balog (2010) found high concentrations of mixtures of organochlorines and lindane even 20 years after they were forbidden in Hungarian and Romanian soils. Whilst the EC has data available on the herbicide applications per country, no data exist on the actual pesticide concentration in European soils.