This article describes the poor environmental and living conditions in Mexico City due to its huge size. Mexico City's size is a challenge to sustainability, and the outcome is unknown. Mexico City and the geographic basin surrounding it included about 18.5 million population in 1995. The basin and surrounding volcanic ranges include nine major environmental zones. Urban growth followed four stages. Different cultures applied different solutions to water supply problems. The basin shifted from self-sufficiency to reliance on 31% of supplies from external watersheds. The water table is declining and canals are polluted. Irrigated agriculture is disappearing. There is an average water deficit of over 800 million cubic meters per year. Mexico City is actually sinking due to groundwater exploitation. There is bacterial contamination of wells due to improper seals. About 75% of the population has access to wastewater treatment and sanitation, but sewage treatment plants operate at under 50% efficiency and treat only about 7% of the total wastewater. Atmospheric pollution from suspended particles has been a problem for decades. Ozone was the most significant air contaminant in 1994. Lead was the most harmful pollutant in 1986. Air pollutants may be the source of submucosal inflammations. Industrial areas are contaminated with suspended particles and sulfur dioxide. High traffic areas have high carbon monoxide levels. Atmospheric pollution has affected the quality of the rainwater. The city survives by importing food, energy, wood, water, building materials, and other products. The development model aims to improve quality of life. The city has been the center of political power since Aztec times, and its preeminent position forces government action. The author concludes that there are limits to urbanization, which the city is approaching rapidly.

Population in 1995 was about 1.2 billion in China and about 935 million in India. Populations are expected to reach respectively 1.5 billion and 1.4 billion by 2025. These two countries now and in the future will average about 35% of total world population. This article compares the current and expected demographic, economic, and environmental conditions in China and India. How these countries manage their growth, poverty, and population will affect the region and the world as well as each nation. China's fertility is now below replacement but population momentum will increase population by about 300 million/year. India's fertility is 3.6 children/woman and India will add 450 million/year. China's population over 60 years old will reach 20% by 2020, while India's will be under 15% in 2025. China will be almost 55% urban by 2025 from 30% in the 1990s, and India will be 45% urban from 27% urban. China's economic growth has averaged over 9%/year compared to India's 5% annual growth during the 1980s and the economic decline during the 1990s. China has 12% of rural population living below the poverty line and India has about 33% of its total population impoverished. China's life expectancy is about 10 years higher. Under-five mortality is 43/1000 live births in China and 131/1000 in India. Poverty-related diseases are still high in India. China is a homogenous population with an authoritarian regime. India is a democracy with a large nongovernmental community and a heterogenous population. India has about 33% of the land area of China but over twice the agricultural land per person. About 50% of China's land and only 25% of India's land is irrigated. Water resources are problems in northern China and much of India. Air and water pollution are problems in both countries. Differences in the population-environment-development context are discussed in terms of the effects of poverty, the constraints posed by development, and the environmental impact of rising per capita consumption. It is concluded that India faces the more difficult future.