Below is an article published by Daily Trust:

The United Nations Environment Programme, which last month [date] released a report assessing the impact of oil spills in Shell's operating area in Ogoni land, has said it will only do follow-up work in the wake of its study at the request of the Nigerian government.

UNEP was reacting to a call by a pressure group calling for a separate investigation of air pollution by oil industry activities in Eleme council area of Rivers state.

The group, Asama Eleme Organisation, charged that UNEP's report on the region was "lopsided", focused mostly on on-site spills, and failed to consider air pollution.

Refineries, a petrochemical company and fertiliser plant, all sited in Eleme, continue to emit contaminants into the air on daily basis, said the organisation's coordinator Jonah Chujor.

In reaction to the claims, UNEP's chief of Post-Conflict and Disaster Management Branch, Henrik Slotte, said, "air quality survey was part of UNEP's overall assessment and Eleme was included."

Slotte added, "Any follow-up work by UNEP, including as part of planning for the environmental restoration of Ogoniland, will be done at the request of the Government of Nigeria."

In an emailed response to Daily Trust Online, Slotte said all stakeholders, local communities, the oil firm Shell and federal government, reached agreement on technical details and what the scope of UNEP's investigation into oil spills in Shell's operational sites across four local government areas of Tai, Gokana, Khana and Eleme should be.

UNEP's report shows high concentration of benzene from petroleum activities in the region. It sampled for various volatile compounds, but focused its report on benzene, because it was "detected in both soil and groundwater investigations in Ogoniland."

Benzene is known to be carcinogenic--causing cancer. Its concentration ranged reached as low as 0.155 microgrammes per cubic-metre of air, but reached as high as 48.2 microgrammes per cubic-metre in some places.

Air quality standards set by WHO were used for comparison but the WHO does not recommend any safe concentration of benzene in the air since the compound is a genotoxic carcinogen--able to cause cancer and alter DNA molecules, inducing mutations.

The highest concentration of benzene on WHO's guidelines is 17 microgrammes per cubic-metre, corresponding to a 1-in-10,000 risk of excess lifetime cancer. Guidelines by the US Environmental Protection Agency uses a threshold between 13 and 45 for the same level of risk.

But UNEP reported that some 10% of samples it studied showed concentrations of benzene higher than thresholds set in both WHO and USEPA guidelines.

It also said nearly all were higher than the concentrations corresponding to a 1-in-1,000,000 cancer risk.

The UNEP also measured concentration of respirable particulate matter, generated when oil burns.

The contaminants have been linked to significant to significant health problems, such as aggravated asthma and premature death in people with lung and heart disease, according to the UNEP report, though they are not the consequence of oil spills.

WHO uses the lowest concentration possible as guidelines since there is uncertainty regarding what extent can have adverse health effects.

UNEP investigators measured two categories of contaminants--particulates smaller than 2.5 micrometres in diameter and those smaller than 10 micrometres--over one-hour periods and compared them to WHO averages for 24-hour periods.