Table 1.

Historical Concentrations of Arsenic in Drinking Water in Northern Chile by Year (1930–1995 Onward)

Region and City or Town	Populationa	Average Arsenic Concentration (μg/L) by Years
		1930–1957	1958–1970	1971–1977	1978–1979	1980–1987	1988–1994	1995 Onward
Region I
Arica	168,594	10	10	10	10	10	10	9
Putre	1,799	1	1	1	1	1	1	1
Iquique	196,941	60	60	60	60	60	60	10
Huara	2,365	30	30	30	30	30	30	30
Pica	5,622	10	10	10	10	10	10	10
Pozo Almonte	9,855	40	40	40	40	40	40	40
Region II
Tocopilla	21,827	250	250	636	110	110	40	10
Maria Elena	6,852	250	250	636	110	110	39	39
Calama	125,946	150	150	287	110	110	40	38
San Pedro	4,522	600	600	600	600	600	600	600
Antofagasta	270,184	90	860	110	110	70	40	10
Mejillones	7,660	90	860	110	110	70	37	10
Taltal	10,101	60	60	60	60	60	60	60
Recent migrants	82,312	<10	<10	<10	<10	<10	<10	<10

^a Population data are based on the most recent Chile census (21).