The Los Angeles Times has revealed the Bill and Melinda Gates Foundation has made millions of dollars each year from companies blamed for many of the same social and health problems the Foundation seeks to address. We speak with the lead reporter on the LA Times investigative team that broke the story. [includes rush transcript]

Is the world's largest private philanthropic organization causing harm with the same money it uses to do good? That's the question hanging over the charity of Microsoft founder Bill Gates and his wife Melinda today. The Los Angeles Times has revealed the Bill and Melinda Gates Foundation has made millions of dollars each year from companies blamed for many of the same social and health problems the Foundation seeks to address.

The Gates Foundation has an endowment of more than $31 billion. The investment mogul Warren Buffet has pledged an additional $30 billion delivered in incremental sums. Since its inception six years ago, the Foundation has committed more than $11 billion to programs around the world. This includes major grants for vaccine and immunization programs, HIV and AIDS research, and public education here in the United States.

But the LA Times investigation reveals the Gates Foundation's humanitarian concerns are not reflected in how it invests its money. In the Niger Delta -- where the Foundation funds programs to fight polio and measles - the Foundation has also invested more than $400 million dollars in companies including Royal Dutch Shell, Exxon Mobil Corp, and Chevron. These oil firms have been responsible for much of the pollution many blame for respiratory problems and other afflictions among the local population.

The Gates Foundation also has investments in sixty-nine of the worst polluting companies in the US and Canada, including Dow Chemical. It holds stakes in pharmaceutical companies whose drugs cost far beyond what most AIDS patients around the world can afford. Other companies in the Foundation's portfolio have been accused of transgressions including forcing thousands of people to lose their homes; supporting child labor; and defrauding and neglecting patients in need of medical care.

Overall, the LA Times says nearly $9 billion in Gates Foundation money is tied up in companies whose practices run counter to the foundation's charitable goals and social mission. And that number may be understated - the Gates Foundation has not provided details on more than four billion dollars in investments it says are loans.

The Gates Foundation refused to talk to the LA Times about specific investments and whether it planned to change its practices. We also contacted the Gates Foundation for comment but we did not get a response.

• Charles Piller, the lead reporter on the Los Angeles Times investigative team that broke this story. He joins us from Los Angeles.