Washington State University researchers have shown that ancestral exposures to the pesticide methoxychlor may lead to adult onset kidney disease, ovarian disease and obesity in future generations.
In fact, this exposure over the past 50 years in North America may be a contributing factor in today's increasing rates of obesity and disease.
The work is also the first to show that a majority of trans-generational disease traits can be transmitted primarily through the female line. However, the researchers did identify mutations in certain genes in the sperm of great-grandchild male rats.
The findings are published online in PLOS ONE.
Methoxychlor - also known as Chemform, Methoxo, Metox or Moxie - was introduced in 1948 and widely used during the 1970s as a safer replacement for DDT. It was used on crops, livestock and pets.
According to the Environmental Protection Agency, methoxychlor was used as an insecticide due to its effectiveness against pests such as house flies, biting flies, cockroaches, and mosquito larvae. It can pass on to humans by inhalation, handling, or ingestion.
Methoxychlor was banned after it was found to mimic the hormone estrogen, acting as a reproductive toxin leading to infertility in animals. It turned up in human breast milk, much like DDT, and it is assumed to be able to cross the placenta. In high doses, it can act as a neurotoxin, damaging an animal's nervous system.
When the scientists exposed gestating rats to methoxychlor at exposure rates found in the environment, they saw increases in the incidence of kidney disease, ovary disease and obesity in offspring spanning three generations.
The incidence of multiple diseases increased in the third generation or "great-grandchildren."
The researchers say the pesticide may be affecting how genes are turned on and off in the progeny of an exposed animal. This is called transgenerational epigenetic inheritance.
The epigenetic mutations that result from transgenerational inheritance can cause entirely different diseases from the hazards to those on exposure.
In recent years, the lab has documented epigenetic effects from a host of environmental toxicants, including DDT, plastics, pesticides, fungicides, dioxins, hydrocarbons and the plasticizer bisphenol-A or BPA.
Because of the altered epigenetics, every cell in the body will have an altered expression of genes, and therefore so will every tissue. For example, the adipose tissue determines to a large degree how your body stores fat. Adipose is highly sensitive to epigenetic changes. If mutated, even a small amount of caloric intake will be converted to fat, leading to obesity.
The EU banned Methoxychlor in 2002 and the US followed suit in 2003. While that ends production of the chemical, any privately owned stocks of the chemical can still be in use, taking years for the banned chemical to be fully phased out.
The pesticide is still widely used in Mexico and in South American countries.