The large sample size and longitudinal nature of the NCS raise unique statistical issues, such as obtaining sufficient samples to provide adequate statistical power to detect health effects attributable to environmental and personal exposures with a minimum amount of burden, while still being cost-effective and staying within the study's overall budget.
What these studies allow us to do is estimate the heritability of an outcome - the proportion of variability in the outcome that can be attributed to genetic factors across a population (and therefore also the proportion attributable to environmental factors).
Debate continues about the degree to which personal traits are attributable to environmental and genetic factors.
Many tumours and cancers are believed to involve epigenetic changes attributable to environmental factors.
Worldwide, 1.7 million children's deaths are attributable to environmental hazards, such as exposure to contaminated water, indoor and outdoor pollution, and other unsanitary conditions, the reports found.
The WHO has reported that 23% of deaths in the developing world are attributable to environmental factors, one of which is pollution, and that environmental risk factors contribute to more than 80% of regularly reported diseases.
For instance, the NCI still claims that 94percentt of all cancers are due to "unhealthy behavior," such as smoking, poor nutrition, inactivity, obesity and over exposure to sunlight, while a mere six percent are attributable to environmental and occupational exposures.
Current evidence is inadequate to establish the proportion of breast cancer cases attributable to environmental pollutants.
Childhood obesity is attributable to environmental changes leading to increased energy intake and lower physical activity.
Rapid increases in disease prevalence are more likely to be attributable to environmental than genetic factors.
This might be attributable to environmental factors and/or plant conditions.
