Both reports point out, however, that effects on health cannot be excluded, because (for example) the studies examined small populations, could not adequately make allowance for other factors which might influence disease rates, could not measure exposures accurately, and could not allow for the possibility of a long latency between exposure and development of disease.A study undertaken by the Government-funded Small Area Health Statistics Unit found a small excess of primary liver cancer near the older generation of municipal solid waste incinerators (MSWIs).